The first thing I did was introduce the "new super-special potty." I loved this one because it was very easy to clean, matched everything, took up little space, and was fairly spill proof even when my little boy was using it.
The second thing I did was have an underwear only weekend. We had them wear only a shirt and underwear and would take them to the potty every 30 minutes or so. Yes there were accidents, but they became much less on the second day, and even less after then.
The third thing we did was offer a reward system. I went to Walmart and bought tons of their favorite charcter stickers and blank index cards. I hung a pocket chart, like the one below, on the wall behind the bathroom door.
When they would use the potty, I would give one sticker for pee and two for well, number 2! They would pick out the sticker, put it on the notecard, and slide it in the pocketchart themselves. I think it was very important that they feel independent and responsible and do it themselves.
Then when the pocket chart was full, I would remove all the cards, hole punch the corner, and attach them all to a metal ring to create a flip book. I would even make a cute little cover out of a notecard that said "potty book." I would keep the potty books in the bathroom on little hooks (or in a basket) and they would "read" them as they went potty.
It worked great for us, and eventhough there were accidents on occasion they were fully independent very quickly.
What's your potty training tip? If you try this one, let me know how it worked out for you!