You need to drink lots of water. Common side-effect of creatine is cramping. But if you drink enough water, you should be able to avoid the cramping.
But everybody reacts differently. I'd drink 2 gallons of water per day, but I still got massive shin-cramps when I jogged. I'd jog for 2-3 minutes, and then it just became too painful.
Also, some people have stomach/digestive problems. One of my friends was puking blood because of creatine.
Just use common sense. Lots of people use creatine without any problems. If you're having bad side-effects, then quit. But it is worth a try, creatine is one of the best legal muscle-building supplements.