We all have at least some moles on our skin. But many of us might not know which moles are normal, and which could be signs of trouble. This year, more than one million Americans will get some form of skin cancer,* and in many of those cases, moles could have served as early warning signs.

Before Amber Holly lets her kids go out and play, they slather on a handful of sunscreen. As a kid, Amber never did. Now, she's had 28 moles removed from her skin - six on her back proved to be cancerous.

"I should have had them taken off before, but I just didn't think anything of it. I can't see them if they're changing colors because they were on my back," says Holly.

That's exactly how so many skin cancer patients get into trouble. Doctors say the neck, back and scalp can be danger zones where cancerous moles often go unnoticed.

"You should really be looking everywhere. If you have a significant other, have that person check you from top to bottom, front to back," says Dr. Maria Riza-Conroy with Ohio State University Medical Center.

If you do find a suspicious mole, Dr. Riza-Conroy says keep five letters in mind - A, B, C, D and E.

"A" stands for Asymmetry - what shape does the mole have?

"The moles that tend to be malignant are irregular in shape. The ones that are benign are rounded," says Dr. Riza-Conroy.

"B" stands for border. If the mole has a rough edge, get it checked.

"C" is color. Moles with more than one color could spell trouble.

"D" stands for diameter. Moles larger than a pencil eraser should be checked. And "E" stands for evolution.

"Evolution means there's a change in the shape, size or color. Or sometimes there are symptoms like bleeding," says Dr. Riza-Conroy.

And remember, time is of the essence. The longer you wait to get a suspicious mole checked, the more likely it is to develop into something more serious.