I used to fly scenic in the Kimberley (Aus) so while it was a long time ago now, I still have to marshal pax to and fro the aircraft. Remember, this is supposed to be fun for you and for them.
First of all, before any pax arrives, brief the other employees/airfield folks near to where you'll be operating as to what you want to do and what you expect. Eg refuelling trucks (if you have them), other pilots, vehicle operators. Ie identify the possible threats before the pax turn up. Know your route to the aircraft and where it's parked.
Stash some sickbags onboard!! Do as much of the preflight before the pax are there. Where are you going to fly? Any gotchas? Check the weather
Clean the aircraft, polish the windows.
Secondly, as others above have wisely said, brief the pax while in the comparative quiet of the office etc what you expect them to do WRT photos/moving between aircraft etc. It's more often than not the first time they'll be around "small aircraft".
Do you have a uniform? Something smart to wear? Something that shows you have some "authority"? The dreaded hi-vis?
2 examples of crowd control walking to the aircraft. 1. walk so fast they have to more or less trot to keep up. (rather amusing to watch). 2. Initially walk in front to point them in the right way, moving to the back to keep them corralled.
Briefing. Practice it before unleashing it. You want to sound confident. Use phrases like "bumps" not turbulence. Make light of emergency stuff but make sure they know when and how to use the exits and seat belts.
If it's a hot day, folks get air sick a lot quicker. Keep a breeze blowing for as long as possible while on the ground, if it's been a bumpy (see what I did there?) arrival and landing, get the breeze going ASAP (window, air con etc).
Remember, don't be afraid to pull the pin on the flight if the weather or any thing else is marginal. There's always tomorrow.