I tried with DD when she was 24 mths. She was a great talker and very curious and interested child (still is aged 7). She had been telling me straight after she'd done a poo for months and enjoyed sitting on the potty. Having fluked a couple of wees and poos in there helped.
After one day in undies it was clear she wasn't ready. She didn't know she was weeing until it was actually coming out and was getting upset about wetting her undies. I didn't want toileting to become a stressful thing for her, so we stopped and tried again a couple of months later.
At 26 months she got it so quickly and easily. Had hardly any accidents right from the first day. I'm sooo glad I didn't push it when she wasn't ready.
She still had night nappies until she was 3. When she felt she should stop having a night nappy I invested in some Brolly Sheets and we went for it. Again, waiting until she was ready made things so much easier.