The use of free weights can dramatically improve climbing performance, especially if you have never trained with weights before. Weight training can be effective for strengthening climbing-specific muscles and developing other muscle groups that can help prevent injury.
For example, pull-ups were for years considered the primary training exercise for rock climbing. Climbers often did lots of pull-ups, and little else. The results were strong climbers, but also chronically sore elbows and shoulders from the repetitive and strenuous nature of the exercise. Balancing a climbing-specific movement like pull-ups with other exercises (for example, bench presses or pushups) helps build opposing muscle groups that can prevent overuse injuries.
It is essential that anyone new to weight training or considering adding a weight training regimen into his or her daily schedule gets more detailed and personalized information than can be offered here. There are many resources available, from books and periodicals to certified personal trainers at a local gym.
Needless to say, incorrect training techniques can do more harm than good. Remember, too, that it takes time to develop an awareness of your personal style, learn how your muscles respond to specific exercises, and find out what works best for you. Gains do not come overnight.
Suggested weight-training exercises to build a basic training program include lat (latissimus dorsi) pulls, bench presses, squats, biceps curls, overhead presses, chest flys, and triceps pushdowns. Exercises that do not require special equipment include pull-ups, dips, situps, and push-ups. Remember that some of these exercises (like pull-ups or dips) are very difficult and may require assistance to complete.