Lately, I have alternated having William in training pants, regular underwear, and diapers. Most days, I'd let him choose. Then after changing wet undies for the 8th + time in a day, I'd put him in a diaper. We would talk about the fact that pee and poop going in the potty and not his pants.
Two weeks ago, I decided that I needed to intensify my attempts at potty training him. So I put him in regular underwear and had him sit on the potty every half hour. We had about 4 successes and about 8 misses. Partway through the afternoon, William told me he wanted to wear a diaper and I told him that he didn't wear diapers anymore. The next day he had 6 successes and 2 misses. It has been up and down with how he does, but on the whole, he's getting better! He even had one afternoon where he went all on his own 4 times! We're up to about 1½ hours between when I have him go and he's usually dry when he wakes up from his naps.
I had gotten this froggy potty awhile ago to make it easier for the boys. It is alot easier than trying to use the "Splash Guard" on our other potty or the ring for the big toilet.
Here he's actually wearing training pants (pink ones at that!) since I hadn't had a chance to wash his regular undies and some of them were missing somewhere at the time!