Re-painting is one of the more simple ways of changing the look of a house, or just a single room. But as with all creative pursuits the choices are often more difficult than the execution. Choosing the right colour scheme is fundamentally important if you want to be pleased with the end result.
It is a mistake to not have any set ideas about a colour scheme. Open-mindedness is usually good, but if you already have a particular room to re-colour you will have to find an option (one of many) that work for that particular situation. It is a mistake to just look at colour sheets and find a shade you like. The shade of colour you choose must suit the room and the other furnishing you have their. It must also suit you. Remember, the furnishings, curtains and even carpets can also be changed to suit the new paint, though this can be an expensive option.
One way to choose room colours that suit you is to look at the colours you use for clothing and other items. You will be spending time in the rooms being painted, so consider yourself part of the overall effect. And consider how you feel with certain shades of colour. If you live in the house, you should be at one with it.
Narrow down the colours you like on the store colour chart to 3 or 4 that you feel are suitable. You can get a small sample pot and paint a 1 foot square area of the wall; see which suit the room best.
Else, take a photo or two of your room under ideal conditions, and use Photoshop to change the wall colours in the image. It may be hard to get an exact match to the store colours, but a photo of the colour chart can get pretty close; you can certainly eliminate some bad choices with this method.
Consider whether you want to modify the rest of the room after the re-painting. Some renovations can be done in two or three stages. You might choose furniture in advance to suit the new colour, or vice-verse; but you have to plan carefully as a mismatch later can ruin the whole effect.