How to weld sheet metal ?

[N.RotaryTech]

So I want to learn how to weld sheet metal.
Some of my projects at home require sheet metal welding, including my FB.
I haven't had much experience with this.
The most recent project I worked on is my Chopper BMX bike. \/


That definitely wasn't my best work. That bike is unfinished, still want to do more with it.

I am currently going to school for welding. But at school we are mostly welding on thick metal.

So at home I want to learn how to weld sheet metal.
I have a MIG welder. I think its a "chicago electric 151." It has adjustable WFS with 4 amp settings provided by switches. (Exp. 35, 55, 95, 120 amps) And of course I have a tank with 25/75% gas mix for it.
I also have a "Hobart EZ tig 165i TIG welder with argon tank.

I'm more experienced with my MIG than my TIG. But I figure the TIG is probably more suited to do excellent welds on sheet metal.

The plan for practice is to go to a salvage yard an pick up a trunk lid or hood off a random car, cut it up, weld pieces together.

So dose anyone have any tips/tricks for welding sheet metal with a MIG or TIG?
Amp settings, gas flow rates, spots welds or continuous beads, etc?