I need some tips on proper welding techniques. I first plan on practicing on some basic mounting trays and stuff first. The kind of stuff that doesn't have to be perfect, but also will be a small project to scrap if something goes wrong. But when I get confident enough to start work on my exhaust system I will need to know what to do as far as encountering dissimilar metals. How do I weld aluminized steel and regular steel together. Do i just need to grind thru the alum. coating on the one side to expose bare metal? What core wire or gas/wire combo is recomended? I plan on practicing with both core wire and gas shielded when building the trays si I can get a feel for both.

Start out by reading a book or two on welding. The AMAZON.COM web store has several good ones at reasonable prices. If you have time, take a class or two at your local community college. For a short cut, go to a local metal supply place and rummage through their scrap bin (ask first) for similar thickness steel and practice on it. Also go to something like:
http://www.hobartwelders.com/talk/
or http://groups.google.com/groups?hl=en&group=sci.engr.joining.welding
and ask serious and intelligent questions. If you do, someone will respond and help you.
I have no knowledge on "aluminized steel" to even suggest a possibility.

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Bob McCormick
69 Malibu project