If you plan to finish your project prior to assembly, be sure to protect the joint surfaces first, so they don't get contaminated by stain and finish. Finishing products seal the wood and prevent glue from penetrating the wood fibers, which it must do to create a strong bond.
Simply push masking tape into the
bottom of the dadoes and rabbets. Then wrap the ends of all the shelves—for 3/8" deep dadoes, wrap the last 1/4" of each end. Blue painter's tape is a
good choice, because it can be left on for long periods of time and
still be easily removed.