If you're currently getting started on a workout program, it's likely you are also considering what supplement to take to improve your gains. One thing you must consider right off the bat is your diet. If your nutrition is poor, you will fail to achieve your fitness goals. Check that out before you consider any supplement.
Below are some common supplements that are proven to be safe and effective for athletes. This info will help you determine what supplement to take and how to take it properly.
Protein is the number one supplement among athletes. Yes, you can and should get most of your protein from your diet. However, sometimes you need a quick and convenient dose after a workout. Some protein powders are specifically designed to be taken before and after workout sessions. By using these, you can optimize your recovery and performance.
Aim to take one scoop before and one scoop after a workout—plus more at various points throughout the day (as needed) if you are unable to get a solid source of protein from your diet.
Check out STACK's Protein Guide.
Glutamine is an amino acid that plays a role in muscle growth, recovery and immune system health. Glutamine levels can be depleted after an intense workout, so it must be replenished if you want your muscles to recover optimally. Aim to take about 10 grams each day, either after a workout or before bed.
Learn more about the muscle-building power of glutamine.
Creatine is one of the most popular supplements among people who want to increase lean muscle mass. It's the precursor to ATP, which fuels each and every muscle contraction. When ATP runs low, contractions stop and your workout comes to a halt. By making sure that you have a full supply of creatine phosphate in your body, you may get an extra rep during an intense set and improve the quality of your workout. (More about creatine here.)
When using creatine, start with 20 grams per day, divided into four five-gram doses. This is the loading phase and should be carried out for five days. After that, take five grams per day before or after a workout.
If you need a quick boost before your workout session and would like to maximize your energy level, consider caffeine. Caffeine will allow you to exercise at a higher intensity level and can also slightly improve fat burn.
Taking 200 mg of caffeine before a workout should be sufficient, but you can adjust this amount based on how it makes you feel. Keep in mind that caffeine can keep you up at night if you take it late in the day. Also, it causes you to urinate more frequently, so make sure to monitor your hydration levels.
 John L. Ivy, Harold W. Goforth Jr., Bruce M. Damon, Thomas R. McCauley, Edward C. Parsons, and Thomas B. Price, "Early Post-Exercise Muscle Glycogen Recovery is Enhanced with a Carbohydrate-Protein Supplement," Journal of Applied Physiology, October 1, 2002, vol. 93 no. 4, pp. 1337-1344.
 Mihic S, MacDonald JR, McKenzie S, Tarnopolsky MA, "Acute Creatine Loading Increases Fat-Free Mass, but Does Not Affect Blood Pressure, Plasma Creatinine, or CK activity in Men and Women," Medicine and Science in Sports and Exercise, 2000, vol. 32 no. 2, pp. 291-296.
 Astorino, Todd A, Roberson, Daniel W, "Efficacy of Acute Caffeine Ingestion for Short-term High-Intensity Exercise Performance: A Systematic Review," Journal of Strength & Conditioning Research, January 2010, Volume 24, Issue 1, pp. 257.