There are several tricks of the trade when trying to make a small kitchen appear larger than it really is.
If you leave a decent gap between the top of the units and the ceiling this will give the impression of more room. When you have wall units going right up to the ceiling it can close the room in and in a galley kitchen layout it would create a corridor effect. If you have enough storage in the rest of the kitchen then having wall units only on one wall will make the room seem wider than it really is. You can leave the other wall blank or have some wall shelves instead as they do not feel as bulky as wall units. As a general rule if you can avoid tall units in a small room this will help and will maximise the worktop area. Reduced depth base units can create a larger area to walk through and are not immediately apparent to the untrained eye depending on the dimensions you choose.
When choosing the kitchen and hardware it is best to use discreet handles or go for a handleless kitchen. A slab door without decoration will also give clean lines and give the optical illusion of space. Along similar lines, if you are tiling a floor use large tiles to reduce the number of grout lines, again giving the feeling of room. The same would apply to wall tiles or you could have glass splashbacks with no/minimal joins for a modern look that is easy to keep clean.
We would recommend using integrated appliances as then you do not have breaks in the kitchen for appliances and it lets the kitchen flow better.
Light is an important factor in any kitchen so it is important to make sure any wall units you have do not block light coming in from the windows.
Once you have designed the new kitchen to optimal effect you then need to maintain it in a way that helps achieve this result you are looking for. To do this it is best to keep the worktops clear, have as few small appliances out as possible when you are not using them and try and remove all clutter from worktops, shelves or on top of the wall units.
An obvious piece of advice but one it would be remiss to not mention when talking about making a small room feel spacious would be to keep colours light. You could also consider gloss doors for the kitchen as these will reflect light better than matt doors.
If you have a small room you wish to make the most of then by all means get in touch for a free no obligation quotation.