"What are the steps to get this working on my iPhone?"
I purchased an used iPhone 3G that had already been activated on the Rogers network (important), was not jailbroken (important) and not unlocked (important). I then purchased a 7-eleven pre-pay phone, and simply put the SIMM chip into the iPhone. Since I rarely make any voice calls, and I don't give out the phone number, my usage is about $3 a month. The deposits are good for one year, and if you refill before the year is up, it all carries forward.
I would also like to get the unlimited Internet browsing for $10 a month from 7-eleven, but so far people haven't figured out how to do this on the iPhone 3G yet. Apparently it works on the 3GS model.
I remains to be seen what 7-eleven will offer as far as a digital data plan goes, and whether it works with the iPhone.
Hint: If you are bidding for an iPhone on eBay, as soon as you see a bid by someone with a 0 history, drop out of the bidding. They are usually there to artifically inflate the price.