Been living abroad for 5 years and some change - in multiple countries, mostly Asia. Including Japan, Thailand and China.
First and foremost, living abroad is a wonderful experience, worthwhile for anyone. The deeper you get into the culture, language and the usual life, the better you'll benefit in later life. I believe it's one of the best crash courses in independence, responsibility, and social skills. So, if you're considering it and feel reasonably ready, go for it.
If possible, I recommend avoiding programs and placement agencies. Programs tend to be insular, meaning you're less likely to have control over your own experience abroad. They have a nice support network, usually, but don't give you as much opportunity to meet and interact with locals as peers. Also, they don't always offer good salaries compared to what you can find alone. Placement agencies just want to fill slots and will misrepresent jobs to meet that. They're very short term industries (speaking from working in one and hating that experience)
Research your city deeply before you go. Public transit, atmosphere, etc are good to know beforehand. China can be hard for people with asthma, or those who are really attached to Facebook or other social media sites, and a lot of people leave because they weren't sure what to expect.
My family has always been pretty independent, so going abroad didn't put much strain on our relationship and I have always been comfortable abroad - so I can't say much about dealing with homesickness. But, with my friends, as I moved to China and dropped facebook - I will say that the friends who found other ways to communicate with me have become extremely close friends and I don't think our friendships will ever break now, tempered as they are. It can be a strengthening experience for familial relationships too.
Best general advice I can give is to avoid expats. If you're abroad, don't waste time spending it with people from your country or culture. Reserve that for when you feel homesick or overwhelmed. I say this knowing people who have lived abroad for up to 10 years and don't speak a word of the local languages because they've just stayed with Americans or whatever.
Feel free to PM me at any time, stranger. Depending on where you go, I can give you some specific advice or put you in contact with some good people. Heck, my school right now is looking for teachers.