Drive around and look at other homes to get ideas for colors.
Remember if you live in an HOA community, you will have to get your paint color approved.
Buy paint samples: This photo shows all the paint samples I bought before I decided on what color to paint my house. Changing the exterior color is a big decision so you want to be sure you're going to love the result. It's better to spend a little money on samples (about $3 each) than not be totally happy with the result.
Paint the sample on more than one location of your house
Look at painted sample areas at different times of day
Remember, painting is a great DIY job. The whole family can be involved. It really isn't difficult (note to self: avoid doing it in south Florida in the summer). It's a rewarding feeling when it's done. And you save a lot of money.
So if your home is in need of paint or you just want a change, go for it!