You know when your child's next doctor's appointment is right down to the hour. But how diligent are you about keeping up with your own health checkups? If you have a Pap smear every year and leave it at that, you're not doing enough, says Dr. Vivian Dickerson, the division director of general obstetrics and gynecology at the University of California at Irvine Medical Center.

"A lot of diseases that begin to develop in your twenties and thirties, like cervical cancer and heart disease, are often silent at first," says Dickerson. "But if they're caught early through screening tests, they may be cured or corrected before more serious complications develop." That's one reason to let your ob/gyn know that you're using her as your primary health-care provider and to make sure that she's comfortable in that role. If she assumes that you also see a family physician or internist, she may not address issues such as skin-cancer and cholesterol screenings during your yearly exam.

If you're between the ages of 18 and 40, here are five important health exams and screenings that can help doctors pinpoint disease early.

1. Breast Exam

Ideally, you began doing a monthly breast self-exam at age 20. If you don't know how, next time you see your doctor, have her show you. Until then, here's a basic description: Lie on your back with a pillow under your left shoulder and your left hand behind your head. With your right hand, use the flat parts of your three middle fingers (not your fingertips) to palpate your left breast. Press firmly around the breast in a circular (clockwise) or up-and-down motion, or mentally divide your breasts into sections and examine each one separately. Now use your left hand to examine your right breast. Next, repeat the exam standing up, making sure to check the armpit area. Finally, do a visual exam in the mirror, keeping alert to any changes in the appearance of your breasts. Remember that breast tissue is full of glands, which can sometimes swell and feel hard, probably due to hormonal fluctuations. Also, some women's breasts are just naturally lumpy. However, it's important that you inform your doctor of any lump or any change such as tenderness, pain, or discharge. She can decide whether a breast ultrasound (to check for cysts) or a mammogram (to screen for a benign or cancerous tumor) is necessary.

How often should you do the exam? Monthly. The best time is about a week after your period ends, since this is when hormone levels are at their lowest and your breasts aren't tender or swollen. If you're not menstruating, due to pregnancy or breast-feeding, do the exam at the same time each month. And starting at age 40 (or sooner, if you have a family history of breast cancer), you should have a yearly mammogram.

2. Gynecologic Exam

A thorough gynecological checkup involves both a breast and pelvic exam. The pelvic includes a Pap smear, an examination of the vaginal walls, and possibly a check of the rectum. With a Pap smear—recommended for all women over 18 and for any girl who's sexually active—the doctor scrapes cells from the cervix to check for evidence of abnormalities, which could indicate or be precursors to cancer.

How often should you have the exam? Once a year. If you have a family history of certain cancers or abnormalities such as ovarian cysts, your health-care provider may wish to see you more often.

3. Cholesterol Screening

The American College of Obstetricians and Gynecologists recommends a blood test to screen for high cholesterol starting at age 45. However, high cholesterol is associated with coronary heart disease, so if you have a family history of heart disease, are more than 20 percent over your ideal body weight, have high blood pressure, or eat a high-fat diet, you should have this test done immediately, no matter what your age. If your cholesterol is above normal, your doctor will likely recommend dietary changes and an exercise program and may prescribe a cholesterol-lowering medication. The most accurate test involves drawing a sample of blood from your arm, then sending it to a lab for analysis. Don't rely on finger-prick tests that give instant results, since they are often unreliable.

How often should you be screened? Every three to five years, if everything is normal. If not, this test should be done yearly.

4. Type II Diabetes Screening

If you're of African, Hispanic, Native American, or Asian descent or have a parent or sibling with the disease, you're at a higher risk of developing type II diabetes—a condition in which the body becomes resistant to insulin, a hormone that is essential in helping the body convert food into energy. The illness often begins gradually after age 40, most often in people who are overweight. It can typically be controlled with diet and exercise. If you fall into a high-risk category, you should have this test done no matter how old you are; otherwise, you can wait until age 45. (This test doesn't screen for type I diabetes, which usually begins in childhood or adolescence, or gestational diabetes, which affects pregnant women.)

How often should you be screened for type II diabetes? Every three years.

5. Skin-Cancer Screening

Regular screenings for skin cancer are recommended beginning at age 18. If you haven't yet had this exam, it's important to do so. Your dermatologist or primary-care physician should examine your skin, from the top of your head to the soles of your feet, looking for suspicious moles, freckles, nodules, or lesions. If, during a self-exam, you notice changes in a freckle, mole, or lesion (it's bigger than a pencil eraser, it develops irregular borders, or it bleeds), tell your health-care provider immediately.

How often should you be screened? Yearly, either by a dermatologist or as part of your annual physical. However, if you have a history of chronic exposure to sunlight (either due to hobbies such as swimming or gardening or because of your job), have had one or more blistering sunburns, or have a family or personal history of skin cancer, your doctor may want to see you more often. Self-exams are recommended at least every three months, more often if you're at high risk.

Dana Sullivan writes about health for several national magazines and is a regular contributor to ClubMom.