Apartments are always short on counter space, which quickly looks cluttered. Put as much as possible under the counter. Paper towel hanger, coffee maker, etc come in under the counter versions. Screw those small white wire shelves on the backsides of cupboard doors to hide things you normally keep out, like salt shakers and pencil cans
:oops: I meant under the cabinet of course
Depending on the size of your apartment, get furniture that fits the place. I lived in a small apartment with a large couch and it was a mistake I won’t make again. Something else that makes a difference is matching furniture. I’m not saying that you have to buy a furniture set but stuff
It might for us to know what your place looks like now. Do you have a lot of stuff, or very little stuff?
I find that having a few things on the wall and a decorative pieces helps. The key work being a few.
Uplighting, dahling…uplighting! Adds drama. Those TV decorating dudes put them in plants and they really look cool. And I think they’re really cheap, too.
Plants. Actual, real plants, in ceramic pots. Silk or plastic ones never look convincing and they gather dust. Real plants transform a room from a lifeless space into a living space.
If you’re not much of a greenthumb, there are lots of hardy varieties that do well in low or artificial light.
…*and *they gather dust. I really need to go dust my rubber tree! But yes, live plants make the place smell better and they do make all that nice oxygen for you.
Well, true. But somehow they seem to gather less. 
One thing my old roommate and I did in an apartment that had one large-ish white wall (we weren’t allowed to paint) that worked out really well: we put up an assortment of inexpensive clocks and mirrors. We used different sizes and styles and shapes and colors, all bought cheaply at Target and Pier One. It looked cool and original, everyone loved it, and it was easy to take down when we moved. The rest of the room was a complete mish-mash of our stuff, but having that one wall decorated intentionally really made the room look fairly put-together.
Think about fun ways to store or organize items. Magazines and newspaper can be stacked in a nice basket (Pier One has many nice ones) and look much better. Continue the theme with a wicker-type ottoman as a side table, with coasters as a splash of color. I don’t mean get a lot of pieces just to have pieces, but* if you have a function to fill anyway*, choose a more stylish way to do it.
What rooms are you thinking about in particular? How do you usually entertain? (sit-down dinners means a fresh set of dinnerware and perhaps a runner, chargers or placemats; cocktail parties means nice barware)
A very nice, quick and easy way to dust you plants is to put them in a cold/lukewarm shower. Or outside in the rain. They’ll thank you in shiny leaves, fresh air and sudden flowers!
This is the best houseplant EVER! Moderate sun, relatively dry.
Google it and learn the love that is the ZZ.