Be ready to go 15mins before the appointed time. This includes warming the engine/s and runups complete, so you can load the pax and go.
For longer flights, have some bottled water and muesli bars etc on hand to pass around.
Ask the customer if they have arranged for transport at their destination, get the number and call ahead to give an accurate eta.
Give a business card to your customer so they can call you if plans change during the layover i.e finished early and heading back to airport etc
S2K