I'm not a social animal so I have to find things to do which are solitary. I walk a lot, take pictures of any pretty or interesting things locally, bake, knit, read, play computer games and do lots of crafty things.
Meditation is very, very hard to get right, but the simplest one I have ever done is simply to sit in a dark (or dimly lit) room with a single candle in front of you, either at eye level or on the floor, depending on how you find it most comfortable to sit. Look at the candle, keep watching it dance and flicker. Don't try to make your mind blank; let the thoughts come, but let them slip away without ferreting at them. Sit quietly, watching the candle, for as long as you wish. When you're ready to return, blow out the candle, let your mind and eyes adjust to normal and carry on with your day/night. It takes a while to stop acknowledging those floating thoughts, but if you can get it down, it's very calming.