There's a really good book out there called "Serious Mountain Biking". It's written by a woman.

When things get steep and gnarly power is not the key. Slow, steady cadence, proper positioning (butt back, back low, arms extended) to keep the front wheel on the ground. Put the bike in a low gear to start and don't try to down shift when getting in trouble.

The Book recommends checking out a tough climb first then making the attempt. And I think practice, practice, practice is the key.