Joe
For steel you want DC Straight Polarity, AC is for Aluminum. Basic rule of thumb is use...1amp per .001th of material thickness, add 30% for inside fillets, and subtract 30% for outside fillets.
Example: .049 Basic = 50 amps, Inside fillet (+30%) = 65 amps, Outside fillet (-30%) = 35 amps. So set your machine up to 65-70 amps and use your foot pedal to regulate the power as you go around the joint.
I like a 2% Lanthanated tungsten, but 2% Thoriated is used by a lot of people. Keep it nice and sharp...easiest was to sharpen is chuck it up in a cordless drill and sharpen while running the drill. Always grind the tungsten lengthwise...not around.
Get yourself a set of Gas Lens Collet Bodies, instead of Standard Collet Bodies, they will make life easier (you can stick the tungsten out further) Go to
www.CKWorldwide.com and click on their technical page and you will find a bunch of useful info there, on Argon Flow, Tungsten size, etc. All good info for you to have. While you are there, check out their Superflex cables, they are great.
Do you Gas Weld? That's a good primer to learn puddle control for TIG.
A Class in TIG won't hurt either...bad habits are easy to learn and hard to change.
Frank