A few things. Your asking this because you're coming to America right?

If that is it, then if you get a burrito, make sure you get it at a taqueria instead of at a proper restaraunt. If you go to an actual sit down restaraunt then get something like beef enchiladas. Restaraunt burritos are basically like enchiladas without the sauce on top. Not like the foiled burritos that are a pound of meat inside one tortilla. That's what you want. Enchiladas are much smaller but they are good.

As for what burrito to get, try a few out. My personal favorite is chili verde without the sauce on top. But if it's on the menu, try out a carnitas burrito. Shredded pork all sauced up, fucking delicious but it's not on to many menus out here and sometimes it is spiced up wrong. But if you get a good one it's tops.

Also, I like to mix my beans and rice up when I get them. Don't know what difference it makes but it makes for a really good side rather then have them separated.