Source: WikiHow

Section 1

Steps:

1) Make sure you know what it means to be Muslim. The first and foremost rule of being a Muslim is believing in the one and only Allah. Allah is the only God, the only Creator and the Almighty. He is the only one you should be doing your good deeds for and the only who shall be worshipped. There should be nothing stood beside His place. Allah's messenger Muhammad (peace be upon him) is the messenger and the last Prophet who came down to Earth, and there will never be any prophets after him. Islam considers itself to be the natural way of all creation. That is, Islam is the original, perfect state of being. So, when a person "converts" to Islam, he/she is actually reverting to their own original nature.

Islam considers anyone who follows its teachings to be a Muslim, regardless of when or where she or he lived. For instance, Islam believes that Jesus was a Muslim, though he lived hundreds of years before Islam's historical founding.
Allah, the Arabic word for God, refers to the same God worshipped by Christians and Jews (aka the "Abrahamic" God). Thus, Muslims revere the prophets of Christianity and Judaism (including Jesus, Moses, David, Elijah, etc.) and consider the Bible and Torah to be divinely inspired.

2) Read Islamic scripture. The Quran is the central religious book of Islam, believed to be the unadulterated word of God and the culmination of all previous Christian and Jewish scripture. Another very important religious scripture is the Hadith, the sayings and accounts of Muhammad. Hadith collections form the basis for much of Islamic law. Reading these writings will give you an understanding of the stories, laws, and teachings that make up Islamic belief.

3) Talk with an Imam. Imams are Islamic religious scholars who conduct religious services inside and outside the mosque (Masjid). Imams are chosen for their knowledge of Islamic scripture and their good character. A good Imam will be able to provide you with advice when deciding whether you're ready to devote yourself to Islam.

Note that the description above applies to imams of the majority Sunni sect of Islam. Imams have somewhat different roles in the minority Shi'a sect.

4) Say the Shahada. If you're absolutely sure you want to become a Muslim and fully submit to the will of Allah, all you need to do is recite the Shahada, a short oral declaration of faith. Be aware that once you have said the Shahada, you are committed to following Islam for life. The words of the Shahada are "La ilaha ill allah, Muhammadur Rasullu llah", which translates to "I testify that there is no other god but Allah, and Muhammad is God's messenger (prophet)." By saying the Shahada, you become a Muslim.

•The first part of the Shahada ("La ilaha illa Allah ") refers not only to deities from other religions, but also to earthly things which can take the place of Allah in your heart - wealth and power, for example.

•The second part of the Shahada ("Muhammadur Rasullu llah") is a recognition that the word of Muhammad is Allah's messenger. Muslims are required to live by the principles of Muhammad revealed in the Quran - the Shahada is a pledge to follow these principles.
The Shahada must be said with sincerity and understanding to be binding. You can't become a Muslim just by pronouncing the words - the oral recitation is a reflection of belief that's held in the heart.
You will never kill, lie, steal, or anything of the sort. In other words, you will follow the Islamic rules.

5) To become a legal member of the Muslim community, have witnesses present at your recitation. Witnesses are not strictly required to become a Muslim - God knows all things, so a Shahada said alone, with conviction, will make you a Muslim in God's eyes. However, to become legally recognized by the Muslim mosque, you generally must make your Shahada in front of witnesses - two Muslims or an Imam (Islamic religious leader) who is authorized to certify your new faith.

6) Wash yourself. Immediately upon becoming a Muslim, you should take a shower or bath as a form of purification. This is a symbolic act that signifies the washing away of the past and of emerging from darkness to light.
No one's sins are too grave to prohibit newfound purity. Upon making your Shahada, your past sins are forgiven. You symbolically begin a new life centered around striving to improve your spiritual state through good deeds.

Take baby steps! Don't go from a baby to an adult! Go from a baby to a toddler to a child and so on! Take your time but remember; Revert to Allah before you return to Hin

Section 2

Steps:

1) Observe Muslim etiquette (Adab). Muslims are required to live their lives in certain ways, avoiding some behaviors and adopting others. As a Muslim, you will keep the following habits (and others):

Observe halal dietary practices. Muslims abstain from consuming pork, carrion, and alcohol. Additionally, meat must be properly slaughtered by an authorized Muslim, Christian, or Jew.
Say "Bismillah" ("In the Name of God") before meals and before doing anything.
Eat and drink with your right hand, and never with the left.
Practice proper hygiene.
Refrain from non-essential interaction with the opposite gender. Remember that all forms of sexual activity outside the the bounds of marriage are forbidden in Islam.
Married women must abstain from sex during the menstrual cycle.
Study and follow the Islamic dress code, which places great emphasis on modesty.

2) Understand and embody the five pillars of Islam. Islam's Five Pillars are obligatory actions that Muslims must take. They represent the core of pious Islamic life. The Five Pillars are:

Testimony of Faith (Shahada). You make this when you become a Muslim by declaring that there is no God but Allah and Muhammad is His messenger.

Performance the five daily prayers (Salah). Prayers are made throughout the day in the direction of the holy city of Mecca (towards the Quiblah.

Fasting during the month of Ramadan (Sawm). Ramadan is a holy month marked by prayer, fasting, and charity.

Giving 2.5% of your savings to the poor (Zakat). It is a personal responsibility of Muslims to help those less fortunate.

Making a pilgrimage to Mecca (Hajj). Those who are able are required to make the journey to Mecca at least once.

3) Believe in the six articles of Faith. Muslims have faith in Allah and his divine order even though it cannot be perceived by human senses. The six articles of faith mandate that Muslims must believe in:

Allah (God). God is the creator of the universe and the only being worthy of worship.

His angels. Angels are the unquestioning servants of God's divine will.

His revealed scripture. The Quran is the perfect will of God as revealed to Muhammad by through the angel Gabriel (Christian and Jewish scripture is also considered holy, they were given from Allah but some or more of the content has already been changed).
His Messengers. God sent Prophets (including Jesus, Abraham, and others) to preach his word on earth.

The Day of Judgement. God will eventually raise all life for judgement at a time known only to him.

Fate. God has ordained all things - nothing occurs without his will or pre-knowledge. Your whole life is already planned

Section 3

1) Continue to read the Qur'an. You can learn much from translations of the Qur'an. Some of these translations may be harder to understand than others. Abdullah Yusuf Ali and Pickthall are the two most common Qur'an translations. However, it's even better to seek guidance from people who are trained in the study of the Qur'an rather than simply relying on your own ability to interpret the Qur'an. Your local mosque will likely have people who will be more than willing to guide and assist you in learning more about Islam and many have "New Muslim" study circles, which are often a good place to start. Be careful, but relaxed, about finding someone who you feel comfortable with and who you are convinced has enough knowledge in order to teach well.
Many Muslims devote much time to memorizing the Qu'ran as it brings great reward. When your Arabic improves, start learning by heart some of your favourite surahs. These can then be recited during prayer or whenever you feel you need a lift.

2) Above all, be the best person you can be. No matter what may anger, sadden or upset you, your duty on earth is to be the best person you can be by serving Allah. Muslims believe that Allah created us to have a good life, and to be happy through our service to Him. Use your talents to help others and better your community. Be open-minded. Never do harm to anyone. Make it your mission to tell people about Islam, emphasizing that Islam is a religion of peace.
Like many religions, Islam advocates that its believers follow the "Golden Rule." Follow the advice of the prophet in the following Hadith:
"A Bedouin came to the prophet, grabbed the stirrup of his camel and said: O the messenger of God! Teach me something to go to heaven with it. Prophet said: “As you would have people do to you, do to them; and what you dislike to be done to you, don't do to them. Now let the stirrup go! This maxim is enough for you; go and act in accordance with it!”

Tips & Notes!

Muslims live as brothers and sisters

Say bismillah before doing anything

Even if you have done many sins in the past, they will not prevent you from becoming a Muslim- when you convert, all your sins are washed away (it is a completely fresh start like you are a newborn)

Islam literally means Salam- Welcome

You must pray five times a day and fast during Ramadan unless you are physically unable to (due to illnesses and diseases) or if you are on your monthly cycle.  Missed fasts just be made up for after Ramadan but not on Eid!

Don't rush into a life of Islam. You need to have a firm understanding of the laws that make a good Muslim before joining Islam. While there is much to learn, these laws should feel natural, as Islam is the religion of the "natural state."
Join the evening/weekend classes at your local mosque to learn more about Islam. Islam isn't just a religion - it's a way of life, providing guidance from birth to death.

Set aside time every day to read the Qu'ran and study Islam - study is a life-long obligation and the more we know about our religion, the more we will benefit.

Try to hang out with pious, knowledgeable Muslims as often as possible - they'll be able to answer your questions casually.

Find out about and adhere to the Islamic dress code - it has many practical advantages as well as helping to identify you as a Muslim.

If you are a female, you should cover your body parts (except hands, feet and face) and not wear clothes that are too revealing or are see-through. Women may want to wear the Hijab (although this isn't compulsory, depending on your particular belief set), a scarf or cloth covering your hair and/or neck. Women must not wear tight fitted clothing. You can wear whatever you want at home, however.

You're never alone - there are many new converts to Islam all over the world. You may be able to meet up with some at your local mosque.

If you realize that you have made a mistake, then sincerely repent and pray for forgiveness, and Allah will listen to you.

Islam is divided into numerous sects. Most people follow the sect of their local mosque, but try to understand the differences between each one. You don't have to follow one, though; if you have a question about a particular action or ritual, just look at the sunnah of the Prophet. If it is narrated (in a narration rated either "authentic" or "good) that he did it, do it. If another narration mentions he did something else, do that as well. It's fine to interchange between actions so you follow more of the sunnah.

Try to be conscious of the Creator and constantly do the best you can where ever you may be.
Always ask a knowledgeable Muslim when you have questions about your newly acquired faith. A second opinion is advisable, possibly from the Imam of your local mosque.

If you can, learn to read the Quran in Arabic. Besides remarkable spiritual benefits from reading in Arabic (even if you don't understand the meaning), the Arabic Quran is the exact words of Allah revealed to the Prophet Muhammad. Additionally, the Quran original is written as beautiful poetry - something that's lost in translations.

If you can't learn Arabic, try listening to the Qur'an recited in Arabic while reading the English translation.

It is vital to perform ablution before salah.

Always try to read books about the Prophets. This will increase your knowledge about Islam and will make you feel better.

Remember Allah at all times not only when you are in need or distress.

Not all Muslimahs wear a veil, depending on their interpretation of the Quran. If you choose not to wear one, that does not mean you can't still be modest.