Obtain color samples from the paint store. Inquire about historic color schemes and any other helpful pamphlets the store might have.
Take the colors home, and determine the ones you feel would best match the brick.
Bring the desired colors back into the store, and purchase a quart of each.
Paint a small portion of the house with the quarts, and wait for the paint to dry. Determine whether you like or dislike the paint. If you like the color, move on to the next step. If not, try again with different colors.
Count the number of doors and windows on your house, and give this information to the paint store employees, who will use it to determine how much of each color will be required to complete the job.
Purchase a quality primer and the highest quality of paint you can afford with a satin or eggshell sheen.