What is the best way to help a good reader master the confusion they have with b's and d's? Here are some suggestions that approach the challenge of differentiating b from d in different ways:
Practice the difference between the letters in a physical game. Let your child practice these letters by writing with their finger tips on different surfaces. Cover a counter top with whipped cream or chocolate pudding. Demonstrate the letters and let the child practice to their hearts content.
Give your child a visual cue for each letter. The b can be drawn as a bat with a ball next to it. The d can be drawn as a dog with a tail. This visual will help your child to remember the shape of each letter and be connected to a picture that uses its sound.
Play with sounds and hear the differences between the two letters. We recommend using the Letter Book inside My Cabin in JumpStart World. Your child can turn to any letter page and experience the letters by listening to the letter sounds, hearing the sounds in alliterative songs, recording the sounds and songs with their own voices, and finally decorating a letter page with stickers of words that all start with that beginning sound.
Make a letter collage by finding pictures of words that start with the sound b or d. Draw the shape of the letter on a large sheet of paper. Then help your child find as many examples of words beginning with the sound as possible and paste them onto the letter collage.
Hang the picture on the wall as a reward and a reminder. These ideas work for learning all letters and sounds, and especially the letters that look alike! 
