My daughter just turned 21 months. She is basically fully potty trained. All I have to do is remind her during the day to use the potty, but I don't buy pull-ups anymore except for nights. She occasionally has an accident at night, and it's just easier and more sanitary b/c she doesn't wake up when she wets the bed.
She comes and tells me when she has to poop, but I also know what time of day she typically goes and that if she lets go a stinky fart it is time to put her on the potty. I can go all day every day with just asking her if she has to tinkle or poop. If she says 'no' then I don't put her on the potty. If she says 'yes' or runs to the bathroom when I ask, then I know she has to go. Sometimes she has trouble going right away, and I say "let me hear the tinkle!" and she makes an effort and begins to pee.
It took some effort and flexibility to get to this point, but she was showing interest at 18 months. I am 8 mos pregnant, so it was important to me to get her potty trained before the new baby arrives, but it is also physically taxing to have to help her get on the potty every time, wait until she goes, wipe and wash hands, and help her pull her pants up. She is starting to be able to pull her pants up and down by herself, but they get stuck on her little chunky butt, and then she gets frustrated and decides it is better to go without them.
You have to be committed to it and stick to a routine, and if you find that something that was working, stops working, then you have to be creative and figure out what will re-engage her.
Start by taking her to the bathroom with you every time you go, and letting her see what you do. Praise yourself for doing a good job whenever you tinkle or poo. Then let her sit on the potty, pants down, and get comfortable there. Put her on every 1/2 hour or so and let her sit for a few minutes. Praise her when she goes, but don't reprimand her if she doesn't. Keep her in skirt and loose-fitting clothes or just underwear. No onesies, they just get in the way.
We started my daughter off on her personal potty, but when the novelty of potty training wore off, she wanted to get up and walk away before she emptied her bladder. I moved her to the regular toilet with a toddler insert and she liked that much better especially b/c she can flush the toilet on her own, and her tinkles make a big tinkle sound. Now I don't even bother with the insert, she just sits on a regular toilet seat. I have no issues with her using public toilets either, she loves showing me that she can go anywhere!
Oh, what you have to look forward to. The first time my daughter said "Poop! potty! Poop!" and we were driving in the car, minutes away from any bathroom, and she was not wearing a pull-up. Fun! that was a mad dash. She has more control over her bowel movements now and can hold for a few minutes while we get to the bathroom, but initially, they don't realize that their going until it's coming out.
Good luck. There are many conflicting opinions on this, but I think earlier is better. Better for the kids to not get used to the feeling of having their waste against them. Better for the environment to not have all of those diapers in land fills, and better for you to not have to change those diapers.