If it's been an hour since my last shower, I shower again.  My Favs have complemented me on my cleanliness when I brought this up.

Or shower with the provider as part of the fun. Not all will want to (makeup, hair etc..) but for the gals that do, I think that makes a great session.

If you are able to shower at home (or at the gym, office, etc,) before the date, then you should only have to jump in for a quick rinse when you get to your appointment. (basically just to make the lady feel better, that you are clean.)

Some ladies are generous with their time and do allow you to go a little over time and not count shower time, but that is not the norm and should never be assumed or expected.