Paint: Many apartment complexes have rules about not being able to paint the inside of your dwelling. If they do, it's probably a boring white / off white color. To avoid the plain bare walls you can paint you're furniture instead. Be creative and paint an old table, wood chairs or an end table a bright color. Paint is cheap, easy and a cost effective strategy to bring color into your home. Another idea, go to a yard sale, swap meet or discount store and find colorful cheap artwork to hang on your boring white walls to bring out the zest.
You could use curtains as a way to decorate you're plain walls without painting or wallpaper. It gives the look of luxury and gives the illusion you have windows behind drapes. Use long drapes that hang from the ceiling to the floor to give height to the room instead of a tiny window or just plain blank wall.
Carpet: Apartments normally don't come with polished hardwood floors many of us dream about; they usually have carpet with three generations of living already built in. Most will have a few stains and you will usually have to live with it. However, there is a solution to the problem and its called area rugs. Area rugs are great for covering stains and boring colored carpet. The best places to find area rugs for cheap are online at Craigslist, Pier 1 and Cost Plus. Area rugs will be your best friend when living in an apartment.
Small Spaces: Apartments are normally small cramped spaces. Using mirrors is a great way to make your apartment feel larger and give it a homey feel. You can find all different sizes of mirrors at a swap meet and/or thrift store. You can find large ones to cover an entire wall if you want, but I prefer many different sized framed mirrors. Framed mirrors give a little extra pizazz and a more extravagant look then plain border-less mirrors. If you like conformity, you can paint the frames the same color or use different colors and/or stain them to your liking.
Dining area: In today's high tech world many people telecommute for work. If you're living in an apartment you may not have the room for a home office. If you need a workspace, one idea is to get rid of the dining room table and replace it with an old farm table or console table that fits the area. This will give it an industrial look and provide an adequate workspace. Instead of dining chairs find some folding chairs that can be folded and stored under your bed. I would use a nice ergonomic desk chair with wheels while working. This will give you the opportunity to use the table as a desk or as a dining table when you have guest.
Furniture Placement: If you're room is large enough you can "float" the sofa in the middle and add a console or low dresser behind it. This can provide a nice barrier between the dining and living area, as they are usually shared spaces. You may have to move it around a bit to get it the way you want it. You may even put up a nice room divider behind the sofa to break it up even more.
Shelving: Shelving can be used in any room of your home and it provides a nice placement for you're what knots or general storage needs. You can use baskets, mason jars and/or any nice containers to sit on the shelves. You can get inexpensive shelving at Ikea, swamp meet or discount store. Floating shelves are really nice and can add an extra flair to any room.