I will answer this question by discussing the risk factors for gallstones and then see whether any of these are preventable.
Age: Gallstones are very common and can happen in any age group from teenagers to the very elderly, however they are most common in the 40's
Sex: Gallstones are more common in females, however occur in thousands of people of both sexes.
Weight: Overweight and obese people are more likely to develop gallstones, although they can still occur in thin people
Cholesterol: Many gallstones are made of cholesterol and hence it could follow that people with high cholesterol may be more likely to develop gallstones.
Family history: as with many conditions there seems to be a pattern of gallstones developing if there is a history of gallstones in the family.
You can't change your age, sex or family history. However if you try to avoid being overweight or having high cholesterol then you may be able to ‘reduce your risk’ of developing gallstones.