Starting Potty Training for a 20 Month Old

There are lots of recent posts about potty training on the site - here is what I posted not too long ago:
I potty trained my son at 22 months after a couple months of wearing pull-ups and using the bathroom pretty often using the "three day method" and I have passed the secret along to many of my friends, one of them had a very stubborn 3 1/2 year old and it worked like a charm, she couldn't thank me enough and was so happy and so was he! I don't know the author, nor does she know that I recommend her method - but you have to pay to download it off the internet. If you are ready and willing to take three days out of your life to potty train I would HIGHLY recommend it! I don't know anyone it hasn't worked for. It just might be the best $24 you ever spent! http://www.3daypottytraining.com/

My advice (and what worked for me) is cold turkey. Tell him that diapers are for night time only and put him in underpants (or as others have said, naked at home). He will have accidents and he will start to put two and two together. Don't make a big deal about accidents. Just say "oops, lets try to make it to the potty next time" and clean him up.
We also had a sticker chart. He got a sticker for each time he didn't have an accident. If he went 7 days w/ no accidents (pee accidents, poo came later) he had a potty party where he invited A family friend to celebrate w/ a pinata and cupcakes. (they brought underpants and swim trunks as a gift) It took two weeks and we were accident free even at night. It took about a month to get #2 down.

Let him be naked at home as much as you can. Take him to the potty "just to try" every 1/2 hour or so. This is the right time to jump on it - he's showing signs. My son trained at 23 months and was incredibly easy. The naked thing was the key for him. In fact, we had to keep him out of underwear for a while - he'd just wear his shorts with nothing underneath! The feeling of undies would make him forget he wasn't in a diaper.

With his big sister I had waited until after 2 1/2 because of big transitions in our lives (adopting her brother, traveling, etc.) and the whole process was much more emotional, much more angst-ridden. I wish I had jumped on it earlier with her instead of waiting. Doing it early with our son was a breeze.

PS - don't fall into the trap of constantly asking "do you need to go potty?" Just say "it's time to try to go potty" and take him.

He is almost at the perfect age, according to Lora Jensen's method in her ebook: www.3daypottytraining.com. I did this with my daughter at 25 months and it has been the best thing ever! I know at least 6 other people who also used this method around the same time as me and they also had success. My daughter just turned 3 and we hit a rough spot (I'm due to have her baby brother in a month) and I was still able to email them and ask questions...almost a whole year later! It's worth checking into!

You may try to make a chart of when he is going to the bathroom. So every time he tells you he is stinky or pees then you can put the time down. After a few days see if there are any trends (like within 15 minutes of each other) then start asking him at those time if he needs to go potty. You can also put him on the the potty a few times a day and see if you get lucky and he goes in there. If he does give him lots of praise.

You can also try to put him in normal underwear so he feels wet or dirty. I had a friend who did this with her son and he went pee once and she said "You need to tell me when you need to pee or you will feel wet and yucky." He was trained after that because he really didn't like being wet. He was a little older than your son (23 months), but if your son knows wet and dirty he should get the gist. GOOD LUCK!