Do you want it to smell like something specifically, or just not smell bad?
I'm mostly afraid of the "smelling bad" part, especially since I have a dog. It basically comes down to "keep your house clean," but these are the things that make the biggest difference:
-Taking out the trash that night if there's any kind of leftovers/meat/meat packaging/dairy/dairy packaging. Don't let it sit and go bad inside your house. -Doing the dishes! Even if I don't think I've eaten anything particularly stinky, even if I rinsed out my dishes...bad smells usually lead to the dishes in the sink. -Keeping fabrics clean. Fabrics hold smells. Wash your sheets/duvet cover/dog beds/curtains/carpets/towels regularly. Vacuum regularly. (Truth be told, I bought a super cheap area rug so that when it starts to smell like dog, I can throw it out without feeling so bad.) -Fresh air! Open windows! -Don't let the bathroom stay humid. -Do your laundry. Even if you have enough clothes to go a few weeks...do you really want all those sweaty, dirty, stinky clothes just hanging out in your room? Like I said, fabrics hold smells. -Wash and brush the dog, if you have one. I'm convinced most people don't groom or bathe their dogs very often because so many dogs are so stinky and oily. I know it's not good to over-bathe dogs, but I think every few weeks is OK. My dog gets it monthly, plus wipe-downs when he's dirty. If your dog is stinky, it doesn't matter how clean your house is. It smells like dog. -If you have a cat, keep the litterbox in the most remote place possible - the garage, the basement, I don't know. I don't have a cat so I don't know the "best practices" but I have a nose and that "litterbox smell" is the worst. If it's in the bathroom or in the laundry room off the kitchen, people can smell it.
I still light a freshly scented candle pretty often. Halfway because candles just feel cozy. Halfway because I'm paranoid that my house smells like dog but that I just can't tell because I'm used to it. And my mom always said fire burns up smells - I don't know if that's true.