A Magical Ending
Often at the end of a session I'll offer a hypnotic suggestion:
Don't be surprised if in the next few days something magical comes from our discussion today.
This can be surprisingly powerful. First, it keeps the subject wondering, or looking back, over the next few days - looking for that magical surprise. So, it keeps it fresh in their minds, giving the session more time to do its work.
This can be especially useful after a weak session, in which the subject ordinarily would have not expected much.
As you may know, the word don't has the opposite effect. It is as if it is a command to do. So, they'll be looking for their own metaphors or isomorphic relationships that match the session in some way.
They usually do find that 'something surprising.'