On training days the time to take your Creatine is as soon as possible after training. At this time, researchers believe exercise primes the body to help best store Creatine (the research). It is ok to take Creatine at other times of day though, it will still be effective.
On non training days, breakfast time, or the time you have your first meal of the day, is another good time. If you would like to help increase Creatine uptake further, take it mixed with a serving of Pure Dextrose or Pure Maltodextrin (or a 50:50 mix of these two carbohydrate powders together).
If you're watching your carb intake and trying to keep it low, then taking Creatine just with a protein shake can also be helpful, or take it at the same time as a meal.