Most breast surgeons I know suggest a self breast exam at the same time of the month, every month. So I am posting this the same time every month so that you get to know your breasts.
Here is a link that will teach you how to do a self exam. It is at the bottom of the page as it talks about all of the options for exam including ultrasound, mammogram, and doctors exam before getting to the at home exam.
If you are over 35 most doctors suggest a baseline mammogram for every woman. Of course if you have risk factors for breast cancer (breast cancer in the family) then you will want to have it earlier, please talk to your doctor about an early mammogram. After age 40 it is recommended to have a mammogram every 1-2 years.