I try my best not to think of my family and friends. What they're doing, etc. That helps. Sometimes, I can't help it and I do think of them and I feel worse, cos I know I can be with them, having fun, doing the things we did when we're together.
In times like that, when I can't help but think about them. I let it be, cos I know that it's okay to feel homesick.
Another thing that helps me a whole lot is never being idle. I don't go out a lot, and even when I do - it's usually to watch a movie with the gals, or trips to Walmart. Even when I'm in my room, doing nothing - I'm usually Facebooking, Youtubing, or chatting on gmail (I'm not a fan of FB chat btw lol). This is something that a lot of my friends do - we don't allow ourselves to get bored and lonely. When you do, you get really depressed and sad, you think of all what you're missing back home, instead of thinking of how amazing the U.S. is - it's truly a horrible feeling.
If you have so much time on your hands (summer break uh huh) - read tons of books, watch TV shows online nonstop, volunteer in the hospital or nursing home (you kill time & it looks good on your C.V. **wink**)
But that's just me. I know some of my friends love calling home - it makes them feel less homesick. Some Skype all day long.
Try doing different things, see what works for you.
Again, it's OK to feel homesick, just don't let it pull you down - LIVE YOUR LIFE!!
Source: Q & A: What do you do when you're homesick? | So You Want To Be Homesick