I learned by the buy a welder and have at it method, hindsite being 20/20 I should have taken the classes 14 years ago and spent a bit more money on good equipment to start with. I'm now (for the 18 months)certified in "structural, overhead, automotive mig welding"
I'm a fabricator at a 4x4 shop in Englewood.

The biggest leaps in technique and quality have come from watching other welders weld. Learning about metals, should come from a teacher and books not trial and error.

Go to a welding shop and ask the manager if you can simply watch their welders weld? Bring your own hood and don't get in the way or even ask a bunch of questions. Watching should get you tons of info.

If you get a quality welder (only 220 units need apply) under the lid where you install the wire is a chart for heat settings and wire speeds for multiple steel thicknesses for given wire thickness. Going by these settings will get you started with the least hassles.

I just bought a Miller 210 and love it, we have 2 of these same units at work. I like the ability to do Aluminum mig welding with it, the boss just let me borrow the spool gun for the weekend I'll let you know how it works on some aluminium.

Get a quality welder. No 110v units.

SD