After stressing about potty training my first I believe I learned one key thing. All the stuff, the systems, they don't really matter. They are just gimicks. They may work with some kids, but it will usually be a struggle. When the child is ready it is ever so simple. So after just this week getting my 3rd child potty trained I can tell you this is my system.
When the child becomes aware that they are wet or dirty and is coming to you independently wanting their diaper changed, this is a good sign. When this starts happening, then I start doing a "test run" once a month or so. This means I put them in underwear for a day to see how long they go between accidents, what their interest level is in the potty, and what their reaction is when they have an accident. The child that is ready to be potty trained needs to be able to go at least an hour in between accidents, be willing to sit ont he potty, and at least be aware that they had an accident if not a bit ambarassed.
If they are going more than once an hour, refuse to sit ont he potty, or don't even notice the accident, they're not ready yet and we go back to the diapers.
When they have shown all those signs it's been about a day of cleaning up messes with each child and then they were done! All I did was tell them each time they had an accident that we needed to do that in the potty, demonstrated going potty for them, and then made a BIG deal out of it when they did finally go. With mine, once they went in the potty once, that was it, they had it. We rarely had any further accidents. (Now away from home in the beginning is really hard as strange potties are scary.)
All kids are different, my first boy trained at 3 1/2 years old, my second boy at 2 1/2, and my daugther that just did it will be three in Sept. But, I think it is absolutely key to do it when THEY are ready not when we want them to be ready!
I know this is long, but I hope this helps some!