I've heard a lot of people say that they wished they had waited until their kids were ready, because it was a lot of frustration and effort on their part, when their kids just weren't ready to get it.
Not saying that this is the "right" way, just sharing my experience. My kids weren't interested at all (despite kid potty books, etc), and I didn't push it until they were 2 yrs 10 mo. I also never bought little potties. My kids are rather tall, and I really didn't want to deal with the mess of little potties. I bought Bjorn potty seats (for the top of the regular toilet) and stools for each bathroom in our house, and a fold up potty seat for the diaper bag to use at a public toilet (really only used that for the first month or two). At that point, I had 2 months to get them potty trained before preschool (which was a requirement). I was really nervous they wouldn't be trained, and therefore not able to go to school. I decided to do the "boot camp" method (for lack of a better term). I knew they were old enough to "get" it, so we went and bought underwear. I picked 3 days where I could stay home with them the entire time, and we didn't have to leave the house. From the moment they got up in the morning, they had underwear on, and only wore pull ups for nap/bed time. Honestly they didn't really understand what peeing was, since diapers/pull ups are so good these days at keeping little ones dry. So they had to learn what it felt like. Honestly, the first day was BRUTAL for me. Lots of little dribbling all day, despite being put on the potty every 30 minutes. Lots of underwear changes, and lots of clean up. I kept them downstairs on the hardwood floors, so that clean up would be easier than on carpet. We talked about it ALL day long. Every time they peed in the potty, they got to choose a wrapped $1 type gift from the basket of gifts I had. This was very exciting as they had no idea what any of them were, since they were wrapped. There was also the intrinsic competition to get one if your twin got one!
They also got a sticker on a chart that I made. I had LOTS of boxes for each of them, and when they filled it up, they got to go out for ice cream (or whatever you think would work for you).
Day 2 - DS had gotten it. The second half of the day, no accidents for him! DD was still having accidents, but it was better than day 1.
Day 3 - by mid-day, DD had gotten it too! I think part of their motivation too (on top of the $1 gifts and the stickers) was that I told them that we couldn't go out (in public) at all until I knew they could pee in the potty and not have any accidents. That was big for them, because they are very social, and always want to out to do something.
Day 4 - I felt so good about it, that we ventured to a friend's birthday party.
Not saying that they never had another accident, but honestly it was VERY few and far between, and was usually the result of playing too long before trying to make it to the potty, and then getting underwear a little wet in the bathroom while trying to get pants down. Pretty good I'd say. Poop was harder, as they would hold it for pull ups for a while, but that just took some more work (and a little bribing!
). It isn't unusual for this to come a little later.
I realize this method won't work for all kids, as they are all different. Just sharing another method that worked for something with twins.
ETA: I switched the $1 gifts for M&Ms (1 for pee and 3 for poop) after about 4-5 days, and then transitioned those out after a couple of weeks, and it was all habit by then. Also, they were poop trained in about 3 weeks.