Long before we got pregnant, a friend and mentor with several children said that she never really pushed potty training. She'd just let the kids run around naked in the backyard in the summer and work it out for themselves. This sunk in and made some sense, and has framed my approach to the whole potty issue.
I should warn you, there's some bold scatalogical detail in here. If you can't take the heat, get out of the potty room...
Our basic approach is something like this:
Phase 1: acclamation. Get him used to the idea that you don't only go to the bathroom in your diapers. Some moms I know report that their kiddos get so accustomed to going in their diapers that they hold it and won't go when the diaper isn't on. So I figured that before he gets too used to those diapers, we'd start introducing the idea of going on the potty.
Phase 2: bodily identification. Slather up that little Irish potato in sun screen, slap on his sandals, and let him loose on our back yard. Let him get used to identifying the bodily signals with the act of going to the bathroom, so he can learn to anticipate his urges.
Phase 3: give him some time to put two and two together. Make going potty a fun and grown up behavior that tickles his innate interest.
The Montessori book I read suggests that children's window of innate interest in potty training is approximately 12-20 months, or starting around the time they are competent walkers. So right around the time Liam really mastered walking and was walking 95% of the time, we headed out to Target to check out some potty chairs.
We ultimately decided on the floor based models because he could get into and out of it himself, which seemed to better support his natural development of independence. Also, they have better pee guards for boys and I didn't want to get squirted in the face while propping him up on one of those toilet-top models.
We started by putting him on the potty for about 15-20 minutes right after he got up in the morning and after breakfast but before his morning nap. We'd just hang out reading books (ones that are only for in the bathroom, therefore "special" books) and playing with some toys. If something happened during that time, we'd celebrate loudly.
This was all greatly facilitated by my friend and our fabulous nanny Ariana (mother of best gal pal Cora). Ariana has done "elimination communication" with Cora (you can google it) since she was little, so she's well experienced at recognizing the signs that a baby needs to go to the bathroom and encouraging going on the bathroom. She had great luck at giving Liam some potty time right after his lunch and before his nap. I'm sure his experiences at her house greatly facilitated his learning curve.
Turns out also that Liam's favorite part of the whole ritual seems to be when we dump the poop into the big toilet and he gets to flush it and watch it swirl down. Its so interesting to watch his fascination with something most adults consider complete mundane and unworthy of note.
In addition to some regularly scheduled potty time, (where we hope to get the timing right so he has to go and can reward the behavior and start reinforcing it), I also try to catch him if I can tell he's got to go. The poops are easier to catch than the potties because his external signals that he's getting ready to poop (stiffening his body, little grunts) are much easier to notice, even if I'm distracted. So if I notice him getting ready to poop I whisk him off to the potty, rip off his pants/diaper, and dash him onto the pot. Generally this works, though twice we've had malfunctions. Once he pooped just in front of the potty on the floor and once he actually pooped half on the seat and half in the bowl. But generally he sits on there looking for all the world like a little man. He reads his books and does his business, and when he's done he stands up (and sometimes signs "all done").
Today was a first, because today was the first time we got an indication that we may be moving into phase 2 or 3. This morning he was sitting by his toy box when he stiffened like he was feeling the urge to poop. He looked up right at me and then started crawling into the bathroom. I scooped him up, pulled down his pants and he sat on the potty and went to the bathroom. Dump the turds, flush the toilet, wash hands and then high fives all around.
I'm sure it won't be easy, but hopefully it won't be as hard as it could be. There's a really cute picture of him on the potty at Ariana's house. I'm sure he'll kill me in the future as a mortified high schooler, but I may try to post it later.