Some people care more about it than others but here are some things you should keep in mind.

While energy/nutrition bars are quick and easy, they can damage overall oral health and your health in general. You should also try to keep a travel tooth-brush so you brush after these types of meals, but if you can't, just brush after main meals.

Piercings - while they do seem cool (and they can be) but they can cause (but are not limited to) easily chipped teeth, a swollen tongue which could cause trouble breathing and/or infections, especially in cases where the piercing equipment is unclean. 

When flossing, you should not be using a sawing motion - this will damage the gums - but you should instead rub it against the tooth.