I placed it in the living room since I have pets and kids and that is the first room you enter in my home. Then I recently bought another because I have a large home and placed it in the dinning area just to have a different scent where we eat and the kids do homework.
I put it in my living room or near my garbage or right by the door where you walk in so when people come in your place always smells nice. Also, if you have closed rooms like a closed closet I recommend putting it in there
I would put mine on a small table in the hall close to the bathroom enterance. And another in the main walk way area. Theses areas are the most used run through throughout the day so this is wear the smell would be most appreciated. ANd the one closet to bathroom keeps the house smelling nice just in case that loved, but forgetful person forgot to turn on the fan or worse, flush!