see lots of cyclists standing whilst going up hills. I can't do this (stand up) is it just practice i need, or am i missing a trick here !!
i can manage about 2 turns of pedals before i collapse
You need to be in a higher gear than if already sitting and pedaling uphill, you're using power rather than revs. It's not essential to be able to do this but it does give another body position and work some slightly different muscles. What helps is that if clipped-in to the pedals you can also pull on the upstroke too.
You are using your arms too however it's important that your arms are helping power the bike by keeping it stable against your leg work rather than wrestle it up the hill as I often see .... that just wastes energy.
Additionally also allows your backside to have a rest/get some air.
I'm not much of a spinner so tend to stand on hills more than most. You can also move with a very low cadence too this way, useful when you run out of gears.