Find a place where you can consistently work out without distraction. This could be your garage, backyard, school or a local gym. Make sure you have access to a selection of weights that fits your level of strength. You may find that you're better off buying a few light dumbbells and working out at home to pump up your arms instead of paying for a gym membership.
Perform bicep curls. This is an exercise that targets the biceps. Perform by holding dumbbells at your side and curling the weights toward your shoulders. Your elbow should remain stable, and you should be using only your forearms and biceps to lift the weights. You can also perform this exercise by placing free weights on an E-Z curl bar. Do three to five sets of four to six repetitions. Perform curls three times per week.
Do push-ups. Performing push-ups is a time-tested way to beef up your arms, while also hitting your pectoral muscles. One advantage of push-ups is that they can be done virtually anywhere. A good regimen for push-ups is to do 10 sets of as many reps as you can. Rest between each set as long as it took you to complete the previous set. Do push-ups at least three but no more than five times per week.
Do pull-ups. Pull-ups strengthen every muscle in your arms and help build definition. You can perform pull-ups on all types of objects, such as a tree limb or a horizontal metal post, or you can build your own pull-up bar at home. Vary the muscles that you target by switching between overhand and underhand grips. Do approximately five sets of as many repetitions as you can four to five times per week.