Not always but if I am interrupted during a brief or doing checklists etc on the ground I put my (inboard!) hand up (palm forward) - this usually seems to convey the message that I do not want interrupting at this stage.
Interruptions seems to be a norm of the age that we live in now. Years ago ground staff were more respectful and would wait and/or pick a better time to talk. To some extent the flight deck is a sacred place and should be regarded as such.