Its a fine art really, after a while you just know when you are getting it right by sight and sound. So really the best advice is practice practice practice.
Main things you need to avoid are blowing holes or not getting enough penetration, the other potential pit fall is not having suficient gas flow to protect the weld from the air and so avoiding perosity, but you don't want to be wasting the gas either. Set the flow rate to about 25 cfh, if you don't have proper gauges a nice hiss will do.
Just play about with it, altering amps and wire speed to see what works best for you, but generally you need everything as clean as possible and make sure the earth is good. Start on thicker pieces of metal rather than thin sheet initially, and just run beads of welds down them. When you are right you should have a sound like frying bacon and a nice pool of weld whilst travelling.
You can then move on to joining bits together, you need to make sure the weld is actually going into the join and fusing the metals rather than just laying on top.
If you master that, go for the thinner sheet, again practice will find what works for you, you can stop start a lot as you go to avoid too much heat and blowing holes, or move the tip around a bit coming away from the weld and back to it. Weaving or zig zagging as you go can help and also helps join the two plates together by giving a wider weld.
Best practice is to" push" the torch in the direction of the weld to better shield the weld with gas but in reality it doesn't make a lot of difference and I Pull as much as push.
One last bit, make sure the welder is as good as it can be, especially the tip of the torch, you'd be amazed at how much difference it makes, as does keeping the shroud around the tip clear of debris. So get a few and change them when they get nasty. A cheapish auto darkening helmet helps a lot now, and try to avoid getting flashed from the arc cos it can be real bad on the eyes.
If you get arceye, it hurts like hell, but cold tea bags help
Now the shouty bit NEVER WEAR CONTACT LENSES OR WELD AROUND SOMEONE WHO DOES, as they can fuse to the eyeball and result in permenent blindness when you try to take them out.....
Have fun and do report back how it goes
