I see far too many climbers who train only by climbing or doing pull-ups to failure. Improving overall body fitness will help much more, especially when slogging into Hallet Peak or the Diamond with a pack to do a route. I think the biggest challenge we all face is finding the motivation to exercise and do some prep work before the season arrives. You will feel better, perform better, lower your chances for injury, and really enjoy yourself much more. If you take nothing else from this article, at least promise yourself to increase your current activity level and to get out and enjoy our gorgeous surroundings.
Motivation is key.
Attend a slideshow, start walking after work with a friend, look at your pictures from last year, call your friends and tell them what heinous rock climbs you guys are going to do this season. Get excited about what lies ahead. If you do so, the more serious commitment to exercise will seem easier and more attractive. I wish to you the lungs of a Sherpa, the strength of a Tibetan Yak, and the flexibility of a yogi. Enjoy your passions as a transformed CMCer, from couch potato to alpinist.