S.H.
My 6 y/o potty trained at 2 1/2 and was completely done in a week. He used the big potty b/c he wanted to be like Daddy.
Now my youngest who is 2 1/2 wants absolutely nothing to do with the potty. The flushing scares him and he refuses to sit on it. I've taken him shopping to buy a little potty and let him pick it out and he just says "No, thank you". So.....guess he's not ready :)
They will definitely show you signs when they are ready. I also bought the DVD "Once Upon a Potty" and think its a great video!