Don't know of any trick? But if you reset the game when there is a camper in the tent/igloo, that camper changes with the reload of the game.
My only experience is when I was plot resetting with a NSF for an incoming villager (& I had someone in the campsite at the same time). It was post update. I would assume it would work the same if you loaded a NSF for the campsite itself. If you liked the camper you saw, you would have to save that NSF to 'set' the game/town. Delete the NSF later.
it works, and if you're getting very few campers with the rate you're resetting at, try the next day. some days campers show up more frequently and some days they don't. it's random though
After reading this, I'm starting to wonder if I've been doing it wrong. I would start the game with a new character, get off the train, and run straight over to the campsite to see if a camper was there. About one time in eight there would be a camper. If there was no camper, I would immediately power off my 3DS and start again with a new character and do it all over again, ad nauseum. If there was a camper, and I wanted them to move into my town, I would then run to town hall. Then I would go through the process to establish the new character, place their tent, and save the game. Then I would start the game over, and delete the new character. That was very time consuming. One time, I sat in an ER and did this trick for seven hours straight without getting a camper I wanted to keep. Is there is a way to streamline the new character/camper reset trick? Thanks for any info anyone would have.