Work the grind as a helper, that is, work with someone that's been field welding for awhile, and go from there, or join a union and make some contacts.  :)

Personally I started driving my rig around to construction sites (bridges, condo sites, highway expansions, whatever) anywhere you see a crane, look for other Rig welders then pull in ready to work and give the job boss your card.  Foundations (pyle driving, shoring, caissons) is an excellent field to get into.  It's hard dirty work, but it pays good.  I wish I had gotten into it years ago.  Whats better than getting your truck all muddy, working outside and playing with heavy equipment all day?!  Look into the Labourers union.  L.I.U.N.A

remember if you want to break out into pipe welding with a rig you will probably need pipe stands , bevellers, flange pins , chain grips , and a few levels too, plus a chain vise is always handy on top of your normal tools when you rig up.