Better start off the list with the most obvious of techniques: paint chips. These colored pieces of paper are free, easy, and effective. The best part is they are made by the manufacturer so you know the color shown is a great representation. However, there are several other factors to consider. Paint chips don’t reflect the finish of the paint or the texture of the wall. It is a small square so it makes it difficult to compare from a distance.
The best goal with paint chips is to determine your final 2-3 choices and buy a sampler of each. Samplers is only $5 and they will end up saving you money in the long run.