In people whose kidneys don’t function optimally, supplemental creatine seems to be safe, too.[513][518][313][528] However, studies in people with suboptimal kidney function are fewer than in healthy people, and they are short-term. People with kidney dysfunction, or at risk for developing kidney dysfunction (e.g., people with diabetes, high blood pressure, or family history of kidney disease; people over sixty; and non-Hispanic blacks), might wish to forgo creatine, or otherwise take only the lowest effective dose (3 g/day)[527] after talking to their doctor.
Another category of muscle-building supplements that lifters and bodybuilders use to improve their results are branched-chained amino acids (BCAAs), or BCAAs. Of the 20 amino acids that make up protein, just three are referred to as BCAAs: leucine, isoleucine, and valine. These are the specific amino acids that have been shown to stimulate protein synthesis and help regulate protein metabolism.
There is a genetic condition known as gyrate atrophy of the choroid and retina, which is associated with a high level of Ornithine in the blood and a relative decrease in Arginine, which causes a relative creatine deficiency due to L-arginine being required to make creatine[478][479] and because high ornithine can suppress creatine synthesis (AGAT) in the glial cells of the retina.[475] This condition can be attenuated by either reducting ornithine in the diet[480] or by supplementing creatine, which is, in this instance, therapeutic.[481][482]
Mercimek-Mahmutoglu, S., Stoeckler-Ipsiroglu, S., Adami, A., Appleton, R., Araujo, H. C., Duran, M., Ensenauer, R., Fernandez-Alvarez, E., Garcia, P., Grolik, C., Item, C. B., Leuzzi, V., Marquardt, I., Muhl, A., Saelke-Kellermann, R. A., Salomons, G. S., Schulze, A., Surtees, R., van der Knaap, M. S., Vasconcelos, R., Verhoeven, N. M., Vilarinho, L., Wilichowski, E., and Jakobs, C. GAMT deficiency: features, treatment, and outcome in an inborn error of creatine synthesis. Neurology 8-8-2006;67(3):480-484. View abstract.
But muscle can’t turn into fat, just like mud can’t turn into gold. If you quit lifting, your muscles mass will decrease over time because there’s no training to stimulate your body to keep it. And your body-fat level will increase if you don’t start eating less (since you burn less). The obvious solution when you stop lifting is to also stop eating so much.
In the last week leading up to a contest, bodybuilders usually decrease their consumption of water, sodium, and carbohydrates, the former two to alter how water is retained by the body and the latter to reduce glycogen in the muscle. The day before the show, water is removed from the diet, and diuretics may be introduced, while carbohydrate loading is undertaken to increase the size of the muscles through replenishment of their glycogen. The goal is to maximize leanness and increase the visibility of veins, or "vascularity". The muscular definition and vascularity are further enhanced immediately before appearing on stage by darkening the skin through tanning products and applying oils to the skin to increase shine. Some competitors will eat sugar-rich foods to increase the visibility of their veins. A final step, called "pumping", consists in performing exercises with light weights or other kinds of low resistance (for instance two athletes can "pump" each other by holding a towel and pulling in turn), just before the contest, to fill the muscles with blood and further increase their size and density. 

Taking high doses of creatine might harm the kidneys. Some medications can also harm the kidneys. Taking creatine with medications that can harm the kidneys might increase the chance of kidney damage.

Some of these medications that can harm the kidneys include cyclosporine (Neoral, Sandimmune); aminoglycosides including amikacin (Amikin), gentamicin (Garamycin, Gentak, others), and tobramycin (Nebcin, others); nonsteroidal anti-inflammatory drugs (NSAIDs) including ibuprofen (Advil, Motrin, Nuprin, others), indomethacin (Indocin), naproxen (Aleve, Anaprox, Naprelan, Naprosyn), piroxicam (Feldene); and numerous others.

Recommended Dose: In Shannon Clark's article, "6 Ways To Get More Energized For Your Workouts", Dr. Chris Lockwood recommends between 1.36 and 2.5 milligrams of caffeine per pound of bodyweight. That would be 200-375 milligrams for a 150-pound person. If that leaves you jittery, try less. Determine your tolerance and find the dose that works best for you.
It is suggested [16,37] that another mechanism for the effect of creatine could be enhanced muscle glycogen accumulation and GLUT4 expression, when creatine supplementation is combined with a glycogen depleting exercise. Whereas it has been observed [38] that creatine supplementation alone does not enhance muscle glycogen storage. Hickner et al [15] observed positive effects of creatine supplementation for enhancing initial and maintaining a higher level of muscle glycogen during 2 hours of cycling. In general, it is accepted that glycogen depleting exercises, such as high intensity or long duration exercise should combine high carbohydrate diets with creatine supplementation to achieve heightened muscle glycogen stores [39].
Those micro-tears that are such a key factor for muscle-building need rest to rebuild themselves and grow stronger. When do they do that? When you’re asleep! “You have to rest and feed your muscles between workouts or you will tear them down and they will become weaker,” says Olson. “Over time, you run the risk of over-training, which can result in injury, and possibly even more sleep troubles.”
Using too much weight, too soon; always start lower than your expected ability and work your way up that first workout. If your form suffers, you are swinging the weight, or using momentum, this indicates you may be using too much weight. Greater momentum increases the potential for injury and reduces the effectiveness to the muscle group being targeted.