You don't have to pull an all-nighter to pass your next medical exam, but that doesn't mean it's okay to arrive completely unprepared. In fact, if you don't prep properly, the test's reliability can be compromised—meaning you may need to have a not-so-pleasant procedure redone, or problems may be missed. In addition to following your doctor's advice, these simple steps can make your next screening go a lot more smoothly.

Mammogram

For the best results:
  • Use a testing facility that specializes in mammograms, and stick with it. Not only will you get to know a few familiar faces, but your results can be more easily tracked and compared from year to year.
  • Skip deodorants and lotions the day of the test. Many contain aluminum, which can show up on your X-ray film and mimic an abnormal result.
  • Ask about your breast density score. Dense breasts can make it difficult to see tumors on traditional X-ray film. If you have a high score (a three or higher), request a digital mammogram—it's better at detecting tumors in dense breasts.

Make it easier on yourself:
  • Don't schedule your appointment during the week just before your period, when your breasts are most sensitive. And take an aspirin one to two hours before the test—it will kick in by the time the mammogram starts.

Pap Smear

For the best results:
  • Continue getting regular Pap smears even if you've been vaccinated against HPV. While the vaccine guards against four virus strains, two of which are responsible for about 70 percent of cervical cancer cases, it doesn't protect you from all types of the disease.
  • Try to schedule your appointment 10 to 20 days after the first day of your period. Blood and cells from the uterus can sometimes interfere with the accuracy of your results.
  • Abstain from sex, baths, and tampon use beginning two days beforehand. Semen can change the pH inside your vagina and irritate the cervix, while baths and tampons can wash or rub away abnormal cervical cells.

Make it easier on yourself:
  • If you have vaginal dryness, it's okay to apply a prescription estrogen-based cream or over-the-counter lubricant to your labia before the exam.

Colonoscopy

For the best results:
  • One or two weeks before the exam, stop taking supplements that contain iron. The mineral can cause black stains that make the colon wall more difficult to see.
  • Cut out red meat and raw vegetables several days before the test. These foods are tough for your body to digest and need time to be cleared from your gastrointestinal system.
  • Avoid grape juice, or foods and drinks that contain red or purple dye, which can mimic the appearance of blood in the colon.

Make it easier on yourself:
  • You may be starving after the exam, but gorging on food can cause uncomfortable bloating—the most common complaint after a colonoscopy. Start off with semisolid foods like oatmeal or yogurt, and avoid gas-producing fare like cabbage and beans.

Skin Exam

For the best results:
  • See a dermatologist. An Emory University study found that dermatologists were able to find thinner tumors than nonspecialists.
  • Ask your partner or a close friend to help you check your skin beforehand, and circle any troublesome spots with a marker. Often patients arrive concerned about a particular mark but can't find it because it's in a hard-to-see area.
  • Remove your nail polish. Acral lentiginous melanoma accounts for about 5 to 10 percent of melanomas, and it commonly develops beneath the nail.

Make it easier on yourself:
  • Avoid taking aspirin the day of the test, and tell your doctor if you're on prescription blood thinners. If he needs to perform a quick biopsy at your appointment, these drugs can cause excess bleeding.
More from Dr. Oz:
From the November 2010 issue of O, The Oprah Magazine
As a reminder, always consult your doctor for medical advice and treatment before starting any program.

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