Great book that I used and was so helpful...Oh Crap Potty Training x
We cracked the main part it in 3 days...still had some accidents beyond this, but didn't feel overwhelming. Son was about just over 2.5 years. Main advice was around start at home naked/half naked if cold and get them drinking loads and just mention it's time to pee a various intervals, rather than asking. Or put them on the potty/toilet if you start to recognise their pee dance. We went underpants free for the first month...just outer trousers. Night times we didn't rush and tackled considerably later. Just remember all children are different and don't put too much on yourself or them x
The hardest part is starting. we went straight into using the toilet with a baby seat on it and I would repeated ask if she needed to pee and take her to sit on it even if she said no. She wore pants in the day and diaper pants at night and we definitely had accidents but she was pretty much day trained in 3weeks.