I learnt by just doing it...
I learnt that it is really hard to compensate a poor quality sleeping bag by using clothes when its sub zero.
I learnt that when your tent leaks and your clothes and sleeping system gets wet and its snowing, its time to walk out and go home.. a day early.
I learnt that I can walk myself so far into the bush that exhaustion can in fact stop me from walking back out that same day as planned.
I learnt to follow a map carefully because bushbashing off track for several hours to only find a dead end (cliff face) leads to exhaustion that can stop you from getting back to your car that day!
I learnt that wet hands and high winds on a cold day hurts.
I learnt that waterproof boots that are getting repeatedly full of water because you are forced to wade through knee deep water holes on a freezing day hurts.
I learnt that well ventilated boots allows freezing cold water to escape really quickly when you need to wade through knee deep water holes!
I learnt that unless your walking partner/s are as enthusiastic as yourself they will whinge and complain and continually ask how long until we are there.
I learnt that sleeping in huts with a group of strangers is the noisiest nights lack of sleep you will ever encounter.
I learnt to only use huts when I they are empty.
I learnt to waste money on 'things' I don't need. Sell those things, repeat.
I learnt that minimal and simple works best for me.
I learnt to be prepared.
I learnt that just because the weather forecast is fine and sunny with a low of 5 degrees doesn't mean it won't rain/sleet/snow and blow gail force winds and end up being minus 5.
I learnt to pitch a tent in as sheltered spot as possible, because when you don't, the wind is going to be well over 50kph.
I learnt to never walk past a good water supply in an area thats known for lack of water.
I learnt to take extra alcohol.
In fact I have learnt so many things I could write a book, I think there is even a whole thread on it around here somewhere. Just get out there and start learning. Read lots, be prepared and go for it