Contrary to popular belief, climbing ability is determined much more by time spent climbing than by natural ability. Most “natural climbers” spend the majority of their training time going up hills. Climbing is hard, even if one is good at it. It is supposed to hurt! Most race climbs are done in Zone 5, so this must be simulated in training. Most of the climbs in races are relatively short (1-10 min.) and very intense. Long, moderately paced climbs to Skyline will help increase aerobic capacity and are good for building strength in the off season, but shorter, high intensity hill intervals are usually necessary for improving race performance. Long climbs are essential if you are training specifically for the Mt. Hamilton RR or something similar.
Doing weekly timed repeats on varying length hills is good for gauging progress. Find a hill in the 2-5 min. range and time yourself on repeats up it. When your times increase by more than 15-20%, it is time to quit for the day. Another good workout is doing intervals up a long, steady climb (my favorite is Hwy. 9). Go 4 min. hard, 4 min. easy all the way up. You can vary the times: try 1 min. on, 3 min. off. The shorter the interval, the harder you go. The effort for each interval should be such that you can barely complete the time. This is good training for the “surging” that goes on in races on longer climbs.
Tactics on climbs in races can make a big difference in your performance. If you are not a strong climber, you should begin every climb at or very near the front. Sometimes you can set a hard (for you) steady tempo at the front and lull your opponents into going at your pace at least for a while. A pace that is moderately uncomfortable will somewhat discourage attacks. Also, if you start at the front, then as the pack strings out, if you start having trouble keeping up, you will have the entire length of the pack to slide backwards before you are actually dropped. If you start at the back, if you open a gap on the person in front of you, you are already dropped. Also if someone else in front of you opens up a gap, you will have to move around them and close it. Otherwise the field will be split and you are in the wrong half!
If you are a strong climber, attack hard from mid-pack on the climb. It is usually better on a longer climb to wait a little until people are already tired before attacking. Quite often a breakaway will happen very close to the top when nobody has the strength left to react. In the case where there is a long descent after the climb however, you should generally attack near the bottom so as to gain as much time as possible on the field before the descent. On a very short climb, such as in a circuit race, it is often a good idea to attack right before the climb, especially if there is a corner. You can get a gap out of the corner, maintain it on the climb and surge again over the top to increase it.