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There are a few things that can be done.

Mirrors are used to give it a false sense of being bigger than what it really is. A well placed mirror can be misleading and seem bigger.

Painting or wall papering the ceilings giving the effect the room is taller than it actually is.

Painting the walls a light color as it reflects the light making it seem more airy. Dark colors make it more cozy.

Pull the furniture away from the wall as it gives the illusion of spaciousness. This gives a more open feel.

The use of stripes in a carpet will help make the room look longer. Your eyes are drawn to different things and creates illusions.

Certain decorations like large vases but not too many. The smaller the item the less impact.

Leave the curtains open allowing more light and it also draws the persons eye fooling the brain how small the room really is.

Obviously if you have a box room there is nothing you can really do except have hidden storage in furniture etc. The less clutter the better.

These are all tricks with light, color and reflection that the professionals use when selling a house or an apartment.






It isn't clear if you are talking about making it look bigger from the outside or from the inside.  

From the outside you can try to remove trees and brush from around the house that makes it look like it is being closed in on.  

There are many more things you can do on the inside to make it look bigger.  

Using light colored paints on the walls will make rooms feel more open and larger than they actually are.  Also removing clutter from the room will make it appear bigger.  If you have too much furniture for the size of the room it is going to feel very cramped and smaller than it actually is.

As others have mentioned, lighting is equally as important.  This ties in to the paint color as well.  A dark room is just going to seem much smaller than it actually is.  Adding as much natural light as possible will make a room feel more open and inviting. 

Finally, this is a personal experience.  If you are able to removing the attic and having vaulted ceilings installed will make a huge difference in how the space feels.  The last two houses that my wife and I have lived in had vaulted ceilings and it was amazing just how much bigger it make the rooms seem.  

Something about the wall and the vertical space carrying all the way up to the peak of the room draws your eyes and makes the house seem much bigger than it really is.

Buy a bigger one :D

Mirrors in general make houses/rooms look bigger (in the inside)

I've a small house and if managed properly you will notice that the house does look bigger. So, to answer this question I'm going to share some of the points I did follow to organize my house in such a manner that it started looking bigger.

Step 1. Foremost get rid of the clutter. Yes, please get rid of the things you are not using i.e they are lying ideal. It, could be any broken stuff so just get rid of that first.

Step 2. Most of the space in house is used by furniture. So, see if you can get compact or a fold-able furniture. There are great innovative products in market. Check on amazon and other websites which are selling furniture - try getting furniture which is compact, and durable.

Step 3. Make use of your balcony efficiently. I've, a 1 bed room apartment with one balcony. So, with help of an interior designer I converted this balcony to a study cum balcony sort of a room. It, servers the purpose of an balcony and at the same time as a place to sit and read in an open space.

Step 4. Re-design your kitchen with latest interiors. This, could be expensive thing but believe me re-designing your kitchen with the latest designs available in the market is gonna save you a lot of space that can be used  for some other purpose i.e. putting in your dinning table there.

Step 5. Eliminate extra cupboards from your bedroom. At times are bed room is stuffed with extra cupboard just have one of them and your bedroom should look bigger.

These were some tips that should help in making a house look bigger.