Performing a self breast examination
A self breast examination involves much more than just feeling for lumps. In order to conduct a self breast exam properly, there are a number of steps you should take:

First, stand in front of a mirror with your shoulders straight and your arms resting to your sides. Carefully look at your breasts, noting the following things:

Size, shape, and color. Your breasts should be their normal size, shape, and color. They should not have any swelling or unusual distortion. Cause for concern that would warrant a trip to the doctor for a mammogram include nipple discharge, dimpling or puckering of the skin, inverted nipples, or any type of redness, be it from a rash or swelling.

After that, you should raise your arms over your head and look for the same changes discussed above.

Now, raise your arms and look for the same changes.

Next, gently squeeze each nipple between your finger and thumb and check for any kind of nipple discharge, whether it's a milky or yellow fluid or blood. Any type of discharge should be brought to the attention of your doctor.

For the next part of the exam, lie down on a flat surface. Use your right hand to feel your left breast, keeping your fingers flat and together. Next, do the same with your right breast, using your left hand. Make sure you examine the entire breast from top to bottom. Start with your collarbone and go down towards the top of your abdomen, then from your armpit to the center of your breasts.

It's a good idea to follow some sort of pattern to make sure you cover the whole breast. For example, begin at the nipple, moving in a circular pattern until you come to the outer portion of the breast. Or, you can move them up in down in rows. Be sure to use a firm touch, so you can look for any kind of lumps in the deeper tissue.

Finally, finally, do the same thing while standing or sitting. This can be in the shower, where some feel it is easier, or sitting up.

What to look for
If you do find a lump, first, don't panic. Even if it is cause for concern from your doctor, 4 out of 5 lumps are benign (or non-cancerous.) If you feel any kind of suspicious lump, see your doctor if:

The breast lump is new or feels different from breast tissue in that breast or your other breast.
The breast lump doesn't go away after your next period.
The breast lump changes in shape or hardness or gets bigger.
You have bloody or yellowish discharge from your nipple.
Your breast has dimpled or puckered