My son is just shy of 25 months and while he started showing interest in the potty at about 18 months, he is not really ready for training. We got him his own potty and let him play with it and on it, and after a few months, he started sitting on it at night with his diaper off while we were getting his bath ready. Took several more weeks before he actually did something. We praised like crazy, and now he'll sit on it almost every night while getting ready for bath, but we don't always have success. Nights when he doesn't want to sit on it we don't push the issue. I take him to the potty a few times a day and if he's agreeable, just let him sit, sometimes success sometimes no. He likes to hand me 'paper' when I use the toilet, and he likes to help me flush, but otherwise no real interest. He doesn't tell me when he needs to go, but he does tell me when his diaper is wet. I don't plan on pushing the issue until he seems more ready - if he asks to use the potty, or can tell me he needs to go before he does it.
I know lots of mothers with young children, and I have found that those who tried to push their kids before they were ready had a much harder time, tantrums, accidents, fighting vs those who just let the kids take the lead. More of the laid back moms kids were potty trained faster when all was said and done. Also, our ped said at his 2 yr visit that he didn't expect our son to be interested in potty training until he was much closer to 3. The thought of getting him out of diapers is exciting, especially with #2 on the way, but I think it would be much easier to just change diapers for a few more months than stressing out over the potty and constantly cleaning accidents!