Daily. I chose not to do a loading phase, but I take 5 g per day post-workout. As I recall, Lyle McDonald recommends that athletes who are trying to make weight for a competition may want to go off creatine at least a month prior because it can make you retain 1-2 kg water weight.
For more information on how to use creatine, I recommend Lyle McDonald Supplements Part 2, which covers the basics for performance supplements. His Supplements Part 1 is also good for general information about vitamins and minerals. Lyle McDonald doesn't talk about a need to cycle off creatine in that acticle, other than to make weight, but I did come across this which makes me think it might not be a bad idea to cycle off for 1-3 weeks like Outlaw mentioned above - "....there is concern that the body may become codependent and cease to produce and store creatine on its own with continued use of the supplement." - Not sure if that's a real concern or not, but I did come across that which makes me think cycling off every couple of months? Just thinking out loud here.
"...It is a naturally occurring combination of amino acids found in meat or fish or produced in the liver, kidneys, and pancreas. The body can build or synthesize creatine using amino acids from the plant or animal protein in foods we eat....creatine is one of few nutritional supplements scientifically proven to increase muscle mass and endurance on a consistent basis, provided that users participate in a regular weightlifting regimen."
"Experts agree that the best animal source of creatine is wild game, including venison, elk, buffalo, and bison. Game meats also tend to have fewer calories, less saturated fat, and more lean tissue than domestic meats. The next best source is lean, free-range meats which include turkey breast, chicken breast, Cornish hens, lamb and veal. Last is wild-caught fish, which has an average of 1-2 grams of creatine per three-ounce serving. Farm-raised fish and animals fed a poor diet have lower levels of creatine."
Hope this is helpful.