People who live in an apartment know that making the best use of space is always an issue. This means making both the best practical use of the space, but also the best visual use; you want to get everything you need in the apartment, but you don’t want it to look crowded.
Light colours make a room feel bigger and brighter; use them for walls and any large surfaces. But is also helps to go the other way with decorations. A light coloured wall with a bold print works well, and gives the illusion of greater space. This also works with a bold coloured piece of furniture. Darkening the space behind a bookshelf is another idea that works well with this approach.
Replica furniture can be quite useful for designing a room, they’re similar to ordinary furniture except they cost a lot less and use different materials.
Concealed storage options are also a good idea. Maximise the use of areas under beds, stairways, side-tables …etc.
Go upwards. Chairs on high legs, think barstools, give the illusion of greater floor-space. Maximising the use of vertical space not only saves you literal floor space, one tall bookcase instead of two small ones, but also gives the illusion that the room is larger and loftier.
Transparent material is less obtrusive to the eye than solid looking items. This significantly reduces clutter. Glass dining tables and coffee tables can be practical and stylish without dominating the room; though glass materials prevent you from storing items inside or underneath them. Mirrors also give a sense of space to a room.
Natural light, which means windows and ceilings, is not only an environment advantage but also a way to make the room seen more open. Look into well insulated designs for windows if you are concerned about efficient heating. Find a way to provide bright and open lighting if you want to achieve an open look at night-time, though some people prefer the apartment to look cosy at this time.
You probably don’t have much choice in the window design of the apartment you live in, but you can always choose the furniture carefully and specifically to create the effect of an open and more spacious apartment. Lighting can always be added to with additional lamps, and a repaint with the right colour might be something a land-lord approves of.