8. Lift like you mean it. If you can do the maximum number of suggested reps (usually 10-12) without feeling fatigued, add pounds (10-15 percent at a time). If you can't complete the minimum number of suggested reps (usually 8), reduce the weight in 10 percent increments until you can. Your last 1 or 2 reps should always feel tough, but doable. (Sept. 1981)
9. Balance your body. To head off injuries, create a more symmetrical look and ensure you have strength for your favorite activities, do exercises for opposing muscle groups. During your weekly routines, if you work the quads, for example, do exercises for your hamstrings as well. The same applies for the biceps and triceps, chest and back and lower back and abs. (Nov. 1987)
10. Take a day off between weight-lifting sessions. Always give muscle groups 48 hours of rest between resistance workouts to allow them time to adapt to the stress you put on them. If you must lift every day, don't target the same muscles in back-to-back sessions. (July 2002)
11. Don't let your routine become rote. To continue to make sculpting gains, change the moves, order, weight, sets, reps and/or rest periods you do at least every four weeks. (Sept. 1998)
2006 Update Try mixing things up more often. According to a study published in the Journal of Strength and Conditioning Research, subjects who varied the number of sets and reps from workout to workout saw greater strength gains over 12 weeks than those who made monthly tweaks.
12. Blast calories with circuits. Do one set of each move in your workout, without resting between exercises. Repeat the circuit once or twice and you'll burn up to 300 calories in half an hour as opposed to 150 from a typical weight routine. (May 1996)