The problem is that this is a vast subject... Alex got it pretty concise there just a few addons..
When you start at (pennies/10 cents) I'd debate that with a deep stack that position means much.. you just hit the flop and play hard.. You can survive on sets, axs and AA,KK.
As you move up (watching Poker trackerstats) you realise that late is more profitable and there's a tendancy to attribute this to winning blinds and having more information. You start raising with strength to take blinds and knock out early limpers with pp's. The late raise tends to get you to the turn for free if you miss the flop. When you add up all the blinds, limpers,free turns and playing top pair sensibly.. you get profit...
BUT... then you move up limits.. and you have to start CBing in late in order to keep up your win rate...
And then you go up a limt and you realise that around the button... CBing without thought and blind attacks... are not as profitable.. so whats your edge?
You'll pick up pretty quick that the earlier you raise - the more respect you get.. and you can exploit this...
Move up limits....earlier raises are all considered as AK and ppl play accordingly... so you start being called down... So you adjust your game and you end up with raises with "interesting" holdings...
The big point as Alex said" is that poker is about the other players... you are taking two risks when you raise early at higher -
1] that you'll meet AA,KK (not really that bad a risk if you're deep) so many ppl re-raise anyway. In fact you WANT this! Why.. well someone with AA WILL usually give you his stack - even if he does'nt hit...
2] who you pick up...
Your mindset changes from a 4bb raise in early being an attempt to win the blinds to " OK- I got a hand who wants to play post-flop?".
4bb from early usually picks out class one hands - with 89 suited you're not that much of an under dog... and the times I've raised early and stacked a guy who slowplayed KK and saw a weak flop
I guess I've also had many put down KK and QQ with a Axx flop fall as well
So many ppl play KK QQ on the assumption that any heavy preflop raise = AK...
As Alex said I do tend to veer away from AK/AQ in early - it is too obvious...(Actually I'm not even too fond of calling heavy preflop raises with these).. I want the WT with AK in late calling me (wit 9Tos) and thinking I'm cb'ing on an unsuited 739 flop
Be warned as you move up.. ppl hook onto the "power" of late - and they will start abusing you
Poker is "all about position" - its also about "all of the positions"
How to learn cheaply
I don't think Americans can do this anymore but some of the most "creative" post flop play and positional play happens on the B2B network - you get ppl all the way down 0.1/0.2 who are extremely good at positional play... They are not loose Swedish drunks by and large - they usually play a very strong post flop game - and they know about position... IMO limit for limit B2B ring is an order of magnitude harder than PS ring...Don't take my word for it look at BW, 2+2 - most B2B threads start - "I have just had my butt handed to me at B2B"