I've found that no matter which machine you use, it's all about the practice.
I grew up on stick machines and when MIG came along I had to have one. Everything I own is Lincoln - it's our closest dealer - so that's where I go for parts / pieces / help. Sometimes they have an in store class where you can meet the pros and ask questions / get help.

What I usually do is before the actual weld is practice on a similar size/thickness piece. But, My only real piece of knowledge that I share with everyone is you gotta be comfortable, by that I mean your body position, things like the weight of the cables can hamper your movement(s) and wear you down making you work harder trying to keep that puddle flowing the way you want it. I always toss the lead over my shoulder so my arm doesn't have to carry that weight.

On youtube there's way to many videos that'll add some helpful knowledge, but you still will need to spend the time fusing metal and getting the experience.