Potty Training: Take 2

I thought teaching was a stressful job. Potty training is definitely a tough and stressful task! We tried some last week, but Jake was so stubborn and did not want to wear underwear or even a pull up. He did however put his underwear on top of his head (see above picture). I even bought him Diego and Disney underwear, but he still wouldn't budge. He also would not tell me when he needed to go and I had to drag him to the potty half the time. So, I decided to take a little time off from it and started again yesterday. He did so good! I told him no more diapers and that he had to wear underwear. He only had one accident the whole day and that was in the morning right when we started. I took him to the potty every 30 minutes. He still has only told us a couple of times when he needs to go to the potty. We usually have to ask him or just take him, but we are getting there. Also, I can't believe that we will be celebrating Jake's 3rd birthday next month! Do you have any tips for successful potty training?