It seems like a jarring transition to go from living far apart and communicating through your phone to actually living and working together, sharing a space, trying to manage social lives in the same location etc.

Depending on your age, the length of your relationship, the time you've spent together etc., lots of couples first decide to live separately and date "properly" before moving in together. Moving to another state or even country is already a huge challenge, as is finding a job etc. These are all factors which can lay heavy on a relationship (and there are many cases where the relationship falls apart).

What are the best things to watch out for? Is there a checklist of things to think about before you make the jump?

You should definitely talk about all the important issues from chores, over finances to eating habits, sleeping patterns, having friends/family over, having your own "space", what to do when you argue etc. etc. It will also help you to talk about worst case scenarios (e.g. what if the one moving doesn't find a job? What if they are homesick? What if you break up? etc. etc.)