Before you hit the beach, or the tennis courts, you lather up-- right?
But are you using the right stuff?

For your health, we break down SPF and answer your FAQ's.

Jenna Glant knows she's supposed to protect herself from the sun.

"I think it's important to wear sunblock to stay looking you," she told us.

For Anet Longo, it's all about health. "I am very concerned about skin cancer."

So what's the right level of protection? Depends on who you are.

Products now offer SPF's ranging all the way up to 70. That's great, if you understand the numbers.

SPF is a universal measurement of UVB rays. An SPF of 15 will screen 93% of UVB rays. A 30 SPF screens 97%.
Not bad, when you consider that an SPF of 2 only blocks half the dangerous rays.

"It surprises me a lot," Amelia Betro told us.

Here are the basics: leading dermatologists like Zoe Draelos, who is with the American Academy of Dermatology, say a 15 SPF should do the trick for most people. That's everyday use, not an all-day trip to the beach.

"This would be for casual wear, you're going to and from your car, you're putting out the garbage, you're picking up the kids at the bus stop," Draelos explained.

But Dr. Elizabeth Hale, who is with the Skin Cancer Foundation, said the numbers mean nothing if the product isn't used properly.

"Studies have definitely shown that people are not using enough sunscreen. In fact, the effective SPF might be far less than what is actually seen on the bottle because people are not using enough," Dr. Hale told us.

That's because it takes a shot glass full of sunscreen on all exposed areas to get the full benefit of the sunscreen. Most people use much less.

For them, Dr. Hale had this recommendation: "If you know you're going to be spending prolonged periods outside at the beach or during the summer time, I say SPF 30 or higher."

And don't forget UVA protection. There's no rating system like SPF, so look for the words "Broad spectrum," and specific ingredients, Dr. Draelos said.

"The most important is avobenzone and two other ingredients titanium dioxide and zinc oxide."

What about using last year's leftovers? While sunscreens are 'good' for two to three years, Dr. Hale said you shouldn't have any!

"If you're really using your sunscreen properly, that eight ounce bottle should not last more than a few weeks. If it's still on your shelf, you weren't using enough in the first place," she said candidly.

So, who should use SPF 50 or higher? Dermatologists recommend them for those who are sensitive to the sun, are taking medications that make them more prone to sunburn, or have a history of skin cancer.

Of course, all the standard sunscreen rules apply: Apply 15 to 30 minutes before you go outside. "Waterproof" doesn't mean you can swim all day and assume you'll still be protected…and everyone should reapply every two hours.

When picking a sunscreen, should you use a cream, gel, or spray? Dermatologists say it's a matter of personal preference but specific types can have benefits for certain parts of the body. For instance, gels dry quicker, which can be great for hairy areas and sprays can be beneficial for tough to reach areas or for balding heads. Creams, doctors say, are still the standby for most body areas.