Take it up. If you can do the maximum number of suggested reps (usually 10-12) without feeling fatigued, add pounds (5-10 percent at a time). If you can’t complete the minimum number of suggested reps (usually 8), reduce the weight in 5percent increments until you can. Your last 2 reps should always feel tough, but doable.
Achieve the right balance. 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 the smaller muscles (biceps & triceps), chest and back and lower back and abs.
Add variety to your workout. Mix up your routine by changing the sequence of exercises. If you always head to the treadmill for your warmup, try the bike. If the elliptical is your favorite, move over to the stairmaster.