A., you sound just like us! First I would say that when kids are really ready, it happens pretty quickly (at least that was ours and our friends' experience). Otherwise, they still don't quite get the feeling of it all, can get nervous and you all will just be frustrated. We got our little girl her potty at 15 months old because she was really interested in what we were doing. She peed once on it at 16 months old and not again for about a year. We backed off and let her just get used to it being there (and collect dust). ;-)
About two months before she turned 2 1/2 she got more interested and started peeing on the potty about once a day. At that point I made her her own potty chart (which she helped pick the colors for) and she was excited about adding stickers to it each time she peed. When she didn't feel like using the chart, so be it, it's hers. About the time I thought it was going to take forever to progress past one pee-pee on the potty a day, she had a big breakthrough and peed all day on the potty and then POOPED that same night!
That's when I decided that we weren't going to buy anymore diapers and when we ran out we were done - that was our biggest breakthrough. She was peeing on the potty more than once a day so I bought a bunch of toddler panties (the Gerber cotton kind with the extra layers of cotton in the middle). I made a big deal about them and let her pick out which style she wanted that day. I bought some pull-ups for nap and bedtime and had to (reluctantly) use them sometimes during the day when she was really having a hard time adjusting to it all. It took about 3 days of her having a hard time not getting to wear diapers. Within a week of no more diapers, she was not using pull-ups during the day unless we were going to be away from the house. A week after that and we could start doing things (like going out to dinner) as long as we kept it within 2 hours (she was terrified of big toilets). We bought a mini Baby Bjorn potty in the car so if we're out for many hours, she could have a place to go potty - she thought that was funny because she gets to "go potty in car" (she thought that's what "potty train" means - LOL).
She did have a bunch of accidents (the most being about 3 changes of pants during the day) but was making it through most days dry. The accidents seemed to really do the trick. She hated wetting her pants, and really started to figure out what it felt like before she went.
She isn't potty trained at nap/bedtime and she wears a pull-up while in bed. I don't expect that to happen for awhile. She was getting up to pee when we switched her to a full-sized bed and staying dry at night. But now that she's used to her bed, she's back to usually peeing at night.
I honestly dreaded the idea of potty training and thought the whole process was daunting. What I have learned is to go with the flow (no pun intended). Let her get used to the potty, don't push things, and reward her when she does go. The two things that really helped us was the potty chart and ditching the diapers when we knew she was ready for the next step. It went amazingly quickly (like 2 weeks)! When we felt like the potty chart did it's part (about a month later), I added the date on the back and laminated it so she has something to hold on to. She's been potty trained for four months and she'll turn 3 in October.
I hope this helps some. But don't worry if it takes awhile. I know our little girl wants to be a "big girl" one minute and plays being a "baby" the next. It's a lot of big changes for them. Good luck and most importantly, have fun! :-)