I think the best thing you can do to become a trainer is to get experience working with dogs. Of course, if you've never done it before, about the only thing you can do is volunteer - but you can volunteer with shelters, rescue groups, assistance dog organizations, some vet clinics, groomers, trainers, etc. You could also apprentice with dog trainers (again, probably with no pay). If you apprentice, I'd suggest apprenticeing with several different types of trainers if possible - obedience trainers, agility trainers, even field trial trainers, etc. The more different trainers you see, and the more different types of training methods you see, the more rounded you will be when you are a trainer, and this can be very valuable. Plus it's a great way to make connections in the industry, and those trainers will become your resource for a possible job and/or possible clients. You will be able to start building your reputation as well as your client pool.
Another option would be to start at Petsmart/Petco. They have decent training programs, and it's a good way to get some experience and learn a lot about dog training. Plus, they have paid training.
While you're doing all this training, you should also be reading all the training books you can find. There are several posts on this forum about books to read, you can search for some. It's also a great idea to go to conferences - you can do some google searches (or maybe there's a listing of them somewhere) and find out what conferences are in your area. If you happen to be in TX, PM me and I'll let you know about several that I know of coming up this fall.
And keep reading Chaz! There are many professional trainers on this forum, and many dog owners that just know a heck of a lot about dogs, and you'll learn a lot just by sitting back and reading.
Let us know if you have any more questions! And good luck!