others have explained this but i will tell you specifically how i do it and have never had a problem [except the time i accidentally put the time to PM instead of AM and ended up with broccolo directly in front of my retail.....].
1. what you do first will depend on whether you know for a fact someone is moving it, have it on good suspicion, or have empty spots and are worried. if i know someone is moving in the next day and choose to do the resetting that morning [less or no TT] or i have a suspicion someone will be moving in today:
1. the first time since 6 am you have played [ie; if i go to bed at 1 am and wake up at ten, its ok that its past 6 am since i havent saved any info from the day yet and as such the layout for move ins is fluid still] load up a NEW SAVE FILE. you cannot do this with an already existing character.
2. run through the creation quickly until you are in a position that you can run around outside and look for the plot. it wont show up on your map.
3. once you find the plot, if its where you want it, go talk to isabelle and then tom nook [put your house somewhere that it wont destroy something you like, you will be able to demolition it after this though] and isabelle again until you can save and quit. then start back up as your new character and demolish their house and you are good to go.
4. if its not where you want it, hit your off switch or close the game without saving and start back over.
however, if its like 8 pm and you just adopted someone from a friends town and want to get their house in order before the morning, you need this additional step before step 1:
go into your game as your normal self and TT to 5:58 AM [!], then immediately save and quit. wait three minutes, then create a new save file. you are at step 1 now. [you dont need to re-tt anymore past this so dont]
good luck
