Remove broken, bruised or dead branches by trimming them at the base with your hedge clippers. These need to be removed for the health of the shrub.
Disinfect hedge clippers before continuing by soaking them for several minutes in a 1:10 solution of bleach and water. Dry the clippers thoroughly before continuing to prevent rust.
Trim back the tips of the shrub to mold it into a desired shape. Scotch broom is a fast grower and will easily get out of hand if not kept in shape.
Thin out the interior of the shrub, removing woody older stems that produce fewer flowers. This encourages new growth.
Trim the shrub again just before bloom to keep its appearance tidy. This should be sometime in mid-summer. -Birdy