As said above, once the body begins compressing from tadpole to frog shape and the tail is shrinking, stop feeding. Once the tail has been absorbed a full 24-36 hours you can start feeding your newly morphed froglet.
This is when you should introduce him to what will be the staple of it's diet - hold off on treats such as bloodworms so they don't become spoiled. They can be like children...too much dessert and they won't like their veggies!