I'm just starting with my 22 month old daughter :D need her totally day trained by march next year hehehe. I got her Dorothy the Dinosaur undies and she loves them, she can hold on for up to two hours. so my advice here is, (I'm aware it has already been said), get undies with his favourite character or item on them :D

My girlfriend told me this a few years ago & I found it hard to believe that it work.

Put a ping-pong ball in the loo & suggest to your son if he can "hit" the ball with his "wee".  If he suceedes awarded him with stickers that he can put on a chart.  Make sure you give him lots of encouragement.  It may take a few tries but it does work.  One more thing, have a small stool, box etc., so he can stand up to the loo.

You may be surprised how much he may love a sticker chart, find some really bright cardboard and make a seven day chart and get your hands on his favourite character stickers have him watch what you are making and let him stick it up by the toilet.  Set a goal (start small maybe twice a day) and if successful he can stick the stickers (we did 1 sticker for wee and 2 stickers for poo).  I also found pull ups or nappy pants did not really work because there was no consequence to the accident, disney undies are great and if they get wet then your son feels what happens when he has an accident. Good luck i know how frustrating a time this stage can be and at the end of the day sometimes you have to accept even though you are ready for this he may not be. Good luck.

Babies are smarter than you think, they can associate behaviour, routines, faces, voices well before 26 months of age. Praise and rewards go a long way. When he does his business, reward him by praise and affection. Don't push him too hard. Maybe even let him sit on there while you read a story and if he hasn't gone by then, then leave it be and try again later.

I have started out just by taking the nappy off at home, when we go out he puts it back on..  He does not like not having it on for the first five minutes, but then gets sidetracked. 

You could try buying him awesome undies with what ever he likes on them.. For some reason my son loves his pirate ones.  

Then every so often you just keep asking him do you want to go. Have some reading material for him. Papa reads on the loo, so he thinks he should too.. :)

He does not always like the idea of taking it off, but is so proud when he does pee where he is suposed to... :) So he is slowly catching on...

Good luck..