To start you have to know where you are in the story. Did you go into their world from your own, or vise versa? Or did you already reside in the same world. Or maybe even did you both end up into an entirely different situation from either of your worlds? If you do reside in the same world, were you two childhood friends/enemies, or did you move there. Or possibly you are there as a transfer to that place and you can only reside there for a certain amount of time. Do something that isn't commonly used for that certain topic and mix match them.

Then there is time. Time is especially important. Like for instance you could do an AU from medieval times and match up your characters to that. Or maybe the 1930's were jazz came up. Or a futuristic world like a post apocalyptic dimension. Or perhaps either of the characters are from the future but ended up going back to your time from sort of event. These different timelines and places can make all the difference in making an interesting story.

Lastly, what type of town are you in? Are you in the country, mountains, coast, big city, or a remotely small town. Is the part of town that your characters live in safe parts or dangerous. These things can make a difference for different scenarios that can come up. Like for instance, a coastal town can have a beach party where the two characters can take a romantic walk on the beach.

When you put these all into effect, then your story won't be the same as everyone elses.