Almost every medical condition is, in some way, shape or form, inherited. As personal genetic sequencing becomes faster, easier, and more affordable, we are going to see more and more people turn to genetic counseling and screening to learn about individual health risks.
In a matter of years we'll have the ability to sequence our personal genome for a few hundred dollars. (Right now it's in the thousands.) If you can't afford to sequence yours just yet, there are a few things you can do until the price comes down.
First, look at what you know of your family tree. Research who in your immediate family ("blood" relatives)--and in your partner's if you have children--has had which diseases or conditions. The resulting list is your first clue as to what you might be susceptible to. For instance, my father had glaucoma, so I knew to be on the lookout for it.
Second, alert your primary caregiver, as well as any specialists you see, to the conditions and diseases present in your immediate family. This information will help target screenings toward specific issues, like early colonoscopy for a family history of colon cancer.
Third, keep close track of lifestyle behaviors that may increase your risk for certain diseases, and make sure your physician is aware. While genetic markers may predispose us to certain conditions, behavior can have a compounding effect, making it even more likely that we will suffer the same fate as our ancestors--or worse. For example, cigarette smokers with a certain enzyme deficiency (a-1 antitrypsin) have a much higher risk for emphysema (although most smokers will develop it eventually).
Finally, do your best to practice basic preventive medicine. As I have outlined previously, the most basic preventive measures you can take are: don't smoke, drink alcohol only in moderation, buckle your seatbelt, and keep your blood pressure, blood sugar, cholesterol, and weight in check.