+1 to what the others have provided in terms of great on-line resources for information.

In addition to bike mechanicals for climbing you also have you. What is your climbing style? What is your current conditioning? Gearing that works for some may not work for your pedaling style. I tend to ride a lower cadence up the sustained climbs than when I am riding on more flat or short rolling terrain, so my bikes are set up with a bit higher gearing than if I only rode hills (not sure that even makes sense).

Also, what do you have for chainring set up? Double? Triple? Depending on your needs, you might need to do both, lower gearing (bigger rear cogs) on the cassette and a smaller smallest chainring on the front.