What are the steps, precautions & parameters to be used for Aluminium TIG Welding?

To clean and preheat the base material properly before welding and apply the  weld with AC polarity according with WPS parameters 

Polarity: Mostly AC / Some people do it in DC too, but i never tried myself.

Tungsten : Balled Shape Tungsten - 2% thoriated (mostly used)

Inert Gas: 100% Argon with flow rate = 15-20 CFH

Gas Cup / Tungsten rod / Filler Wire Size can be selected based on base metal thickness.

Follow the AWS Code D1.2 & you can get prequalified base & filler metal combination. 

Tig Welding Aluminum is pretty cool!

First of all, not everyone who can Tig weld, can Tig weld aluminum. Its one of those things that really sets a welder apart .

Although nearly all metals can be TIG welded, the metal most frequently associated with the TIG welding process is aluminum, especially when we are talking about Tig welding thin gauge aluminum.

Aluminum can also be mig welded, but in the lighter gauges the best process is usually TIG. (some folks even gas weld thin gauge aluminum)

The popularity of tig welding in automotive, hot rods, and chopper applications has brought TIG welding to a new popularity.