Everything I've ever read by Machka is spot on target, but may I offer another secret of climbing? The secret of climbing for me (47 years old, 230 pounds) is: pedal fast.

At the flat before the hill, I'm pedaling at 85 rpm in my highest gear. As I begin to climb, I'm focusing on maintaining my pedal speed, and shifting gears to allow me to continue pedaling at 85 rpm, plus / minus 2.

As the climb steepens and I can't maintain my 85 rpm, I progressively switch into a lower gear that allows me to maintain 85 rpm. Just keep shifting into lower gears so I can maintain 85 rpm.

If the slope drops and pedalling becomes easier and I see my rpms tending to climb, I decide to either 1) pedal slower to stay on target or 2)shift to a higher gear to go at a faster speed and drop the rpm to 85.

I often climb at 85rpm/4mph, and I know I've been at 85rpm/3.5 mph, but for me it's not the speed, it's the rpm. And at higher rpms you're not going to blow out your knees or your lungs, you're just using the mechanical advantage you've invested in. And climbing at 85rpm, with a 19 gear-inch combination, just isn't that much hard work- it's sustainable, moderate effort.

So I suppose the Unified Theory of Climbing accomodates alternative techniques.
As long as you're riding up the hill, it's all good.
Cheers,
Ed