Here are a few tips:
Always buy a sample, the smallest samples in most stores is a pint of paint, Just buy it, paint your paint on a poster board, or if you can, directly on the wall. Leave it there for a couple of days. Paint on a paint chip never looks the same on the wall, as it does on the chip.
It is worth you money, you don't want to have to re-paint an entire room, or worst case scenario your entire house.
During the last project a pretty coral colored paint chip turned out fluorescent pink. It was the only color we didn't get a sample of . Luckily the painter had only just started. We were able to stop him. Buying a sample saves you money in the long run!
Also paint a smaller sample like a box top or piece of poster board. This is the sample I would carry with you while shopping for bedding and furniture. Its amazing how things come together when you carry a little inspiration with you. I also try to carry fabric swatches with me while shopping too.