Most important thing to remember is safety. I saw a video on youtube of a guy welding with two 20lb propane bottles only about 3 feet in the background. Also, saw a couple videos of welding next to a lawn mower (gas).
Dude(s), what are you guys thinking????
Also, undestand what issues you have with out gassing when welding various materials, like galvanized or zinc plated steel pieces. Also, wiping down with some solvents (Chlorinated Brake Parts Cleaner) to clean the pieces will generate nasty gasses like fosgene (sp?) that can kill you on the spot. Not to mention the pair of Harley jeans I perforated when playing with the plasma cutter (they do sell fire retardent jeans and pants).
Always ventilate the work area, use protective clothing from UV and Sparks, and keep 2 fire extiguishers handy. One near the welder, and one near your point of exit from the area, in case things get out of hand.
Another best kept secret, is that Plasma cutters usually operate at a higher voltage than welders, and can be lethal. I prefer to ground the workpiece directly and always use gloves on both hands. Obviously, insulated shoes, not leather soles, which conduct if damp (feet do sweat).
Hot metals from welding take a long time to cool down. Usually not lethal, and a lesson that is quickly learned and retained.
Everlast PowerPro 256 (2013)
Northern Hybrid 200 & ST80i
HF 90Amp FluxCore (Don't laugh, it is what got me started)
Lotos LT5000D Plasma
HF 4x6 Horizontal Bandsaw
Rikon 18" Bandsaw w/VFD
Delta 14" Drill Press
Robland NLX31 Euro Combo WW