DO- have your bridal party wear their shoes to rehearsal. I was in a wedding at a golf course and you could not have your heels sink into the grass, so we had to "pretend" we had our shoes on and walk on our tip toes during the whole rehearsal. Also it just makes it easier if the girls are standing on uneven ground that they get the feeling of it in their own shoes.
DO- be on Time. Especially if you are having your rehearsal at a different location than the rehearsal dinner. You never know how long it may take and if there may be traffic to get from one place to another.
DO- have the music there. Whether it is a DJ, or someone playing an instrument. It helps with timing to make sure the music is on cue with the procession of the bridal party.
These are my top three that I feel can make the rehearsal go a little easier.