Mark
Kitesurfing is a very natural extension to surfing, as most of the guys here have said it is a dangerous sport and when you think that the kite has enough power to drag you around the water just like a ski boat, thats a fair bit of power in your hands.
The best way is to have lessons from a qualified instructor, New generation kites are a lot safer than a few years ago and wood-orge is right about flying the kite as its about 80-90% of kite surfing. If you cant get lessons in your area there are a few good instuctional DVD,s but beware of the dangers in the spot, there have been fatilitys over the years and every season people get injured/hospitialised learning to kite surf.
Know with the warnings out of the way. Kiting rocks it has ruled my summers and winters for the last 7 years, I am just starting to get over the addiction now, be warned if you get into it and get hooked many an hour will be spent chasing wind and waves.
As for boards many crew are using just there old surfboards either with straps or without, sure they will break after a while but they are good enough to get you out there and on the water without the expense. cheap functional twintips (wakeboards) can be made out of plywood in a few hours (no glass) and can get you on the water quick and cheap.
Kites the new generation bow kites have almost 90% depower and are very stable but as in all new gear they are expensive. You should be able to pick up a 2nd hand 4 or 5 line kites for 1/2 to 1/3 the price of new
This is what i would do if i had to start again
A) drive around your area until you see some kiters, have a chat to them to get a handle on local conditions, safe beginer spots, sources for lessons and gear.
B) by a small trainer kite, this can be just a cheap two line stunt kite and rig it up on a bar with short 10-15m lines. Fly this until you can do it with you eyes closed, the steering action is a bit different. Fly it hooked into a harness.
C) Get an instructional DVD or mag and watch it again and again
D) get a lesson or two well worth the money for what you will gain and safety knowledge
E) buy the right sized kite and get out in a safe learning location ( sandy beach uncrowded large downwind area with no obstructions x-on wind no more that 15 knots and shallow if possible)
F) get out there and do it, learning curve is steep but quick.
Cheers
PS did I say get a lesson…