Man,, so much of this is saddle time. It can be hard to explain unless we are in the field with you, watching you..
Know the phrase, "Chopping Wood", that's spinning pedals and not getting power on the ground that moves you forward.. You've got to learn to shift Into your power stroke and that for most of us is a cadence, a good spin, for me 80 'ish RPM. When I started 60 was about it. I never seem to need more than 90ish now.. no idea why.
Going UP hill,,, depends,,
For short punchy climbs I pick a gear before I go up that keeps me from chopping wood and I stay In It,,This can be trial and error,, you need to do drills.
For Say longer 25 foot sorta steep climbs, I come up to/at those balls to the walls 'MID Cassette' and on the big chain ring going for all the speed I can muster.
I start up and get about 10 feet then as my cadence begins to fall I drop a ring up front and stand and hammer,,,,,,for about 10 feet......
Then I drop to the granny ring and I stand and hammer, hopefully for about 5 feet,,,climb complete
I NEED my 3 X 9 I NEED those big gear jumps up front,,some don't..
I tried a 1 X set up, It taught me alot but for my trails and my abilites and my bike weight 2 X 10 or 3 X 9 only for me.
Remember my cassette ? Its in any middle gear, sorta,,say 3rd cog or 4th'ish, I don't shift that while doing a steep climb because my speed will fall off to fast while shifting,,,as soon as I get to the next lower gear its too late for that gear,,,click pedal click pedal click and your stopped, the gears are too close..
I pretty much do all my roller flows in one gear..say the 4th or 5th cassette cog and my middle up front,, unless they are fast rollers the 6th or 7th on the cassette. The game of the roller flows is NOT to need to pedal at all !
Google Pumping the bike or pump track..
Sitting in the saddle and mashing hard can and will hurt your knee's,,fixing them is a real bad deal...
Seated climbing helps you spin and In 'Spin' you have power, just like a car engine..
Standing and pedaling is fine IF and ONLY if you can accelerate or hold speed with NO pain and I hope your clipped in for this kind of balls out climbing..
Think seated for long climbs and standing for short or punchy climbs as In BURST of power...
You gotta find one big nasty hill out in the open and learn to get up that thing so fast none of your friends can catch you..
Intervals,,google that.
A good way to do this,,find a pretty steep hill, but not too steep,,you should be able to run up It without touching the ground with your hands,,
Start running up and down it Untill you puke..twice a week... If It gets easy carry the bike on your shoulder,,and a full pack,,till you puke..
Google point of failure exercising ...
Decide now,,are you a man or a mouse,,your gonna have to commit..
No pain no gain...
NOW onto corners,, next post... I need a beer..