I have three boys, and the two oldest started showing interest at about that age too. The first was done (except at night) by two years old, and the second seemed to be done, then decided to re-do the diaper thing until right before three. Then, I just told him it was time to go potty, and had him potty at intervals aroudn waking, sleeping, etc.. My youngest is now two and 1/2, and he too started showing an interest at about 20 months. A mom of four told me when my youngest was interested that she had noticed a window of interest at about that age, and that if you followed up on it, it usually made it that much easier . . w/my experience, I would agree. I haven't worked w/my two year old as much, and have plans to really do so this spring/summer when it is warmer. I will say, w/my older two, it was such a breeze just to follow their lead and run w/their interest. And you don't have to teach them standing up. All mine have sat, you can even sit them backwards, so they get the idea they potty facing the toilet. That helps w/the larger toilet. And when he uses the smaller potty, my youngest likes to dump it and flush it himself, making him want to use it more.
Hope this helps, A.