I recently started learning how to weld for an A-level Design Technology project. (Well, that's the excuse, anyway!
). The following site seems very useful:
http://www.tpub.com/content/construction/14250/index.htm
Start at chapter three. It seems to be a manual for US Navy fabricators.
# BUYING A WELDER
Obviously there's no substitute for hands-on-experience. I'd recommend you buy a stick welder (shielded metal arc, not tig!); you can pick them up fairly cheaply and they're most fun (MiG just seems like cheating because you don't really have to do anything apart from pull the trigger).
Places I suggest you look to buy a welder:
o Ask around - see if anyone will be willing to let you have an old welder cheaply.
o Check out the Freecycle group in your area (they're on Yahoo! somewhere). It's surprising what people are willing to give away.
o Try and make friends with an 'insider' - one of my friends has a bunch of welders he was given from one of his engineer mates; they failed a routine safety check and he was supposed to destroy them, but they seem to work fine. I take no responsibility if you die though!
o Obviously you can also buy one - this is probably the best idea for starting out because you know the welder actually works! I bought mine from Screwfix.com for £50 (about $90), but they only sell within the UK.
# OTHER EQUIPMENT
I'd STRONGLY recommend buying the following in addition to a welder (in no particular order):
o Obviously you'll need a face mask
o A set of clamps. I bought these from Screwfix:
http://www.screwfix.com/app/sfd/cat/pro.jsp?id=18295&ts=77717 . They are immensely useful for holding stuff together and save you having to fiddle with G-cramps and stuff.
o Welding gauntlets. They protect your hands when you forget that the metal's red hot and you try to pick it up, and they also protect from the spluttering molten metal.
o An angle grinder. I know it costs quite a lot, but it saves you having to cut welder fodder with a hacksaw which means you get more done.
o A chipping hammer. You need this to chip the slag off the weld.
o A magnetic work holder, for example:
http://www.screwfix.com/app/sfd/cat/pro.jsp?id=16535&ts=77717 . It becomes very useful when you start learning fillet welds and stuff.
# STARTING TO WELD
If you buy a welder new, you should get an instruction manual with it. This will tell you information on work thickness against electrode thickness against welding current required. Here's the welder I bought, there's a link to the instruction manual near the bottom of the page, just in case you need a manual:
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=100333&ts=78590&id=80274 .
I suggest you start by learning to lay a bead on some relatively thick stuff (say 5mm thick). I learnt on 1mm (18 ga) and by the time you've got the metal to flow, the base metal has got a hole in it. Unfortunately my project is in 16 ga so I have to learn to cope with that!
That's about all I have time for at the moment, I'm afraid. If you want more information, just reply to this and say what you want to know. Please be aware that I AM NOT a professional welder. I've only been teaching myself on and off for a couple of months. I'm sure there will be professional welders on here who will be more than willing to help you out.
Good luck, and enjoy your welding!