The prevalence of dementia is expected to increase dramatically over the upcoming decades due to the aging population. Since treatment is still short of a cure, preventative strategies are of the utmost importance. Stimulating activity (cognitive, physical, and social), vascular risk factors, and diet may be important in preventative strategies. Dementia risk may be modified by participation in stimulating activities. One study suggested that the cognitive, physical, and social components of activity were of equal importance to cognitive outcomes. However, while exercise interventions appear to benefit global cognition, the benefits from cognitive training appear to be domain specific. People with vascular risk factors (hypertension, diabetes, dyslipidemia, and obesity) appear to be at higher risk for dementia than those without in observational and clinical trials. Controlled trials suggest that vascular risk management via some pharmaceutical interventions may benefit cognition, though results are inconsistent. Finally, people who adhere to a Mediterranean diet or who have high intake of antioxidants and omega-3 fatty acids have reduced likelihood of dementia in observational studies. However, supplementation in controlled trials has not generally proved successful at improving cognitive outcomes. A single supplement may be insufficient to prevent dementia; it may be that the overall diet is more important. Future large randomized controlled studies should examine whether interventions can reduce the risk of dementia and whether combining cognitive, physical, and social activity, vascular risk reduction, and dietary interventions might have additive or multiplicative effects.