How do you teach a 3 year old to recognize the urge,

[annex]

I was anxious about this as well with my 3 yo DS, and scheduled a special conference with his preschool teachers before school started. The school required "potty trained" as one of the conditions of enrollment. They basically laughed at me and said it was totally normal, and they have all the class go potty at certain times (e.g. right before morning snack, right before playground time, etc.) This will keep most of the non-initiators dry as they work on this skill. It's good though to make the teachers aware, so they keep a close eye on your DS for any potty dancing, etc. in between the normal schedule times.

[hoodlims]

I wouldn't worry about school! Anyone who works with 3-5 year olds will be taking the kids to the potty frequently, plus there will be peer pressure!