Lately one game organizer faced an angry landowner because during an outdoor game some players passed the road on her property. This could have been avoided by three actions beforehand. 

Briefing- written and spoken by the instructor. We have previously written about safety and how to map the risks. One aspect of briefing the game rules to event participants is to remind the safety aspect. It is also worthwhile to add a sentence or two in the game info/welcome text. The content of the reminder depends on your local conditions and notes about weather, traffic, natural obstacles might be relevant. But one aspect of such reminder is throwing in a sentence about not to intrude on private property. “Respect the private property and don’t intrude even if some location is set there” will suit well.  

Testing. Setting up a game is quick with Loquiz. Ideally, when you have set up the game and pins to new positions, you should test the full game outdoor. This way you are sure the locations are indeed safe, accessible and tasks appropriate to the surroundings. Testing the game takes a fairly small chunk of your time and has multiple other benefits.

Consent. If you know that your game is going to have a lot of pins on the private land, then contact the person and ask permission.