1. Make sure you don't grow your tribe too fast. Just because the villagers can make lots of babies doesn't mean they should. Your villagers shouldn't have more babies than your food source can handle.
2. Have at least 2 villagers trained in Medicine so that if one doctor gets sick there is a second one to heal everyone.
3. Have at least 2 villagers trained in Farming.
4. Whenever you are going to be away from the game for more than an hour or so, it's safer to quit the game, rather than to leave it running. (Wise words from LadyCFII)
5. If you don't paused your game at night, try leaving it at 1/2 speed.