It is going to depend a lot on where you are planning to go.
I'm an expat and have lived in China, Colombia, Panama and I now live in the Philippines. Every one is very different with entirely different required knowledge.
There are the obvious questions like what language will be spoken. Keep in mind that claims of a large English speaking populace are usually wrong. More often you will find a few people who speak some English. In China (2 years) even the English teachers didn't really speak at all well and mostly knew parrot phrases which they didn't really understand.
In Colombia there were a few more but not many, Panama was the same.
I speak Spanish, but the fact is that every country speaks a different Spanish and even different local twists can throw you.
As an example; in the US and Mexico a standard greeting is "que pasa" basically what is going on? In Colombia saying "que pasa" will get you into trouble really quick because you are saying "what are you up to?" in an accusatory way. Even if you can get it across that you didn't mean it that way you will be distrusted until they really get to know you. There are a million of these "little rules" that you just have to learn.
You are also, depending on location, going into a strange physical world with hazards that you may not be accustom to watching for. This will be far more true if you are talking about going into the 3rd world and if you are going as an example to the tropics from cooler climes.
As for books I will through in a shameless plug and suggest you read my book "How To Become a Smarter Safer Traveler" I'll be happy to send you a free copy if you send me a private message at Borsiawriting@Yahoo.com, be sure to put something in the subject line so I don't accidentally delete it as spam.
Other books would be specific to the region you want to move to.
Do a lot of research and be sure to take extended exploratory trips before you break ties or make any serious commitments. Changing countries is an expensive venture in the best of times doing it repeatedly even more so.
it is very hard to know if you have a good fit until you have been in a place for an extended time. Often what seems really nice gets old after a year or two.