Uphill Bike Riding - Mountain Bike Zen
Uphill riding position
In general riding uphill on a mountain bike you will need to remain seated. This will keep your rear wheel firmly on the ground and does dramatically increase traction so more of your pedalling effort goes into driving you and your bike uphill.
On very steep sections you will need to lean forward too, if you raise your butt off the saddle you rear wheel may be prone to spinning out and this could cost you momentum and lead to a dismount...then you're walking till it gets less steep and you can get back on and get going again.
On lighter inclines not much else is needed, but on steeper inclines you also need to use your arms to pull on your bars and keep your front wheel hard into the ground and gripping firmly.
Gears and suspension
You need to choose a low gear for pumping uphill, get into gear before hitting the slope, riding uphill and changing gear will put extra strain on your gears and chain which is to be avoided if possible, it is much better to be changing up than changing down while riding uphill. Don't be ashamed of using granny gear (your lowest). It is better to keep a slow, balanced and steady pace throughout a long uphill than it is to try and race it to hard and end up without enough stamina to get to the top. Walking is for hikers not bikers!
If you have lockout on your suspension you will want to engage this, particularly for the front suspension, on longer climbs to stop the front wheel bobbing around as this will take out your uphill momentum and cause steering problems. It is usually not worthwhile to disengage your suspension between short climbs and descents.