Well, you may already know how to do this, but I think it’s useful advice, nonetheless.
When you are making a burrito, spread your fillings evenly across the tortilla and fold in the sides. Now simply take the bottom and roll it all the way to the top. That is a burrito. If you are going to split this with someone or you simply like your PB&Js, cut down the middle, cut the burrito diagonally (generally, this is called a French cut as it pertains to vegetable slicing. I’m not really sure if it has a name for things like this, though.)
When making a simple wrap, just spread your filling evenly, fold up the bottom, and roll one side all the way to the other. Just make sure your filling doesn’t come out of the top. You also want to make sure you didn’t leave too much space at the top, or else your first few bites are just going to be tortilla. If you don’t have much filling, just place it a little off-center giving more to the top (but not so much that it all falls out), and then fold accordingly.