I know a lot of people are waiting til their kids are 3 to train them, but I started training both of mine before age 2. dd10 was totally trained at 21 mos. We got the potty video when she was 18 mos. and put the potty chair in front of the TV. I used pull ups when we were out in public or at daycare, and training pants with plastic pants at home. Several other kids in the daycare were training at the same time, so she wanted to go just like them.
Unlike most kids, mine both trained for #2 first, within only a couple days, but it took a little longer for them to be consistent at holding #1. There's nothing wrong with accidents, it's a learning experience. A 3 year old might learn faster, but that doesn't mean that a 2 year old can't learn, it just may take a little longer. If it gets to the point that it's totally stressing you or your child out, then take a break for a couple weeks and try again.
DD7 would only pee in the potty about half the time at age 2. I knew she knew when she had to go, but she wouldn't take the time to do it if she was busy playing or something. The week before she turned 2.5, I told her, you're going to be 2.5 next week. After you turn 2.5 you can't pee in your panties anymore. You have to use the potty every time because 2.5 is too old for pull-ups. That's all it took was for her to know I was serious and what I expected of her, and she never had another accident.