A.S.
Mine two are 16 & 13 . . . both boys. They are very good, well-adjusted kids with friends and "lives." But they both love to be at home too, and they seem very open with us.
IMHO the best thing we have done to avoid problems so far is just spend ALOT of time together as a family. When you are highly invested in your kids, and they know it - it makes a huge difference when they are teens. That's not a relationship that can be built overnight - when they are little is the time to get it going. To a child love is spelled "T-I-M-E."
Another thing that I think that has been helpful (sounds odd) - board games. That gives them insight into adult thought process and decision making. We have had some great discussions just out of games.
Good luck and try not to worry (easier said than done, I know). Stay close with them now so they'll have confidence in you later.