Arnie Baker has some good tips on climbing in his book "Smart Cycling"
a summary:
seated climbing is the most energy efficient. climbing out of the saddle takes strength in the arms as well as the legs. it takes more energy, but you have more power. try to direct your energy to those legs, and not waste energy on needless arm motion. however, standing while climbing relieves saddle soreness, and provides a change in position that can be helpful.
thus, if you want to attack, or you are in danger of being dropped and need extra power, standing can help -- just as wehn you need that power spurt in a sprint. if you don't have the gears to spin up a hill, you may have no choice but to stand, even though it is not the most efficient way to climb.
when seated, baker recommends getting your bum far back on the seat, and pushing forward on the pedals, rather than down (think of a leg press in a gym). concentrate on pulling up as well as pushing.
he suggests the most efficient cadence is between 50 and 70 (which seems pretty wide to me); however, he mentions that the fastest way to climb, if you are strong enough, is to push the biggest gear you can.
he also advises to set a rhythm and stick with it, rather than trying new things mid-hill. especially breathing: consistent and steady.
hope this helps...it helped me.