The brighter, longer days have a tendency to make rooms that looked cozy a couple of months ago, look a little too lived in now. Halls are particularly important as you need to consider the effect you will achieve when standing in the hall, looking through the doorway into the room beyond. To give depth and richness to room, look for areas and sections to paint in other, similar shades of the main colour. For example when you have chosen your main colour, paint any recesses in a subtly different colour, try painting the ceiling or cornice a tone or two lighter or darker than the walls, and perhaps the window frame in a bolder, darker complimentary colour.
Light is one of the biggest factors in choosing a colour.
When using tester pots, paint decent sized bits of your wall at various points in the room, and round a corner if you can. This will indicate what effect that light will have on the colour you choose. For a contemporary look, avoid gloss paint and go for a matt or semi-matt finish instead. For an easier and less smelly painting experience, water based acrylic eggshell is rapidly becoming the most popular choice - and its less harmful to the environment than oil based ones. Feng Shui may often be derided as 'loony land', but check out the basics before finalising your room layout - most of the principles are plain common sense for achieving a comfortable and harmonious living environment.