[ratdude747]

for TIG, a trick I was taught once was to put the (pointed) end of the tunsten rod (make sure it is the "green" kind, not orange or red) about .25" INSIDE the porcelain gas shield...

also, for TIG, make sure you are set to AC, not DC if you are welding AL.

For any metal or welding type, be sure to use a wire brush to get the weld areas as oxide-free as possible... having an angle die grinder/drill with a wire brush makes this a lot easier.

Last, for TIG, this is kinda a basic thing, but make sure that you use the correct filler rod. for butt and inner angle joints, the thickness should match the thinner of the two edges being welded. for lap and outer angle joints, no filler rod is (generally) needed; sometimes it helps to "cheat" and use a bit of filler rod to get the puddle started.