There are many ways to teach a child to use the potty. I will tell you what I have found to be generally helpful for most children. After a child shows an interest in using the potty; tells you before or even after the fact that he/she needs to use the potty; and/or can accurately report on poop or pee (I keep the terms simple), then it is time to start using the potty. I suggest wearing diapers during the first week of using the potty. Be sure to have an ample supply of loose pants with elastic waist bands and shoes with velcro tabs. After you have taught your child how to (basically) dress him or herself, loose the diapers during the day. The child gets a really clear message to pay more attention when the pants are wet or soiled. Yes, it is messy, but it is also very effective. I would rather clean up the mess and just get on with the training. Of course the child has to change the clothing. I help if I see an earnest effort.
Needless to say (can you tell I am about to say it anyway?), there should never be any blame or shame when the child has an accident. You could say: “Oh, I see you had an accident. I think next time you will go to the potty when you feel the pee or poop getting ready to come”. Try to think of some way to encourage (not praise). Encouragement notices some part of the child’s effort -whether or not that effort has been successful. Encouragement is a means to stimulate desired behavior. Praise is a reward we dole out for a perfect performance. Praise and encouragement both have their proper time and place (it is actually a whole other topic). It will take some thought and attention on our part, but remember that encouragement is much more important for the sake of your child’s self esteem. One other point - it is common for the child to loose interest after a few weeks. Be prepared to just start over when the interest returns. DO NOT RUSH!