1. Good process for thin metal ‹ very clean process producing good looking welds.
2. Use Argon shielding for steel, stainless, and aluminum.
3. Use DC-Straight Polarity (DCEN) for steel and stainless. Use AC for aluminum.
4. Always use a push technique with the TIG torch.
5. Match the tungsten electrode size with the collet size.
6. Aluminum ‹ use a pure tungsten, AWS Class EWP (green identifying band). Will form a balled-end in AC.
7. Steel and stainless steel ‹ use a 2% thoriated tungsten, AWS Class EWTH-2 (red identifying band). Prepare a pointed-end for DCEN welding.

http://www.welding.com/technical_welding_tips.shtml#mig