Well, this is really a tip for true noobs, but here goes:
When climbing a hill seated (assuming you have the sense not to be grinding up in a huge gear), if you start getting tired, you may wish to stand in order to exercise a different set of muscles. When you do this, shift up a gear or two. I know, you're dying already and you don't feel like dialing up the pain. But if you switch to a standed climb at the same cadence as your seated spin, you're going to waste a ton of energy keeping that pedal speed. Try it.