You will need some pre and post flow to protect the tungsten. .5 seconds for pre and enough post that the tungsten is no longer red before it stops. About 10 seconds per hundred amps is a good starting point. A good frequency to start at is 100-120. Balance at 30 is fine. The arc will be a lot different than DC, so don't expect something as smooth and quiet. Be sure you have good argon flow. With a #6 - #8 cup, around 15-20 CFH (7-10 lpm) is a good start. Use a foot pedal if you have one so you can start and end at lower current.
Long arc, short arc, heliarc and in-the-dark!