I work with Kinder, 1st, 2nd and 3rd grade students who often times confuse the letters b, d, p and q. We have come up with a chant and some images that help us remember which is which.
b = a /b/ /b/ bat is a /b/ /b/ "b"
d = a /d/ d/ doorknob is a /d/ /d/ "d"
p = points down, a /p/ /p/ pickle is a /p/ /p/ "p"
q = points down, a /qu/ /qu/ quarter is a "q"