Patience
It takes years and years to develop an aerobic engine.
If it is a long climb, try to be the one setting the pace at the start. Eventually the stronger climbers will go harder and you will fall off the back. Don't go much over threshold until you get towards the top and then empty the tank. If you expend you W' or FRC to early, you are done. Try to catch on the descent. (Assumes we are talking real climbs)