like cool kale said, avoid eating too much salt. that doesn't mean you can eat anything that's not salty. check for sodium content of the food and avoid anything that has high amounts of sodium, like ramen, chips, etc. drink a lot of water but do not drink too much because too much fluid intake also increases blood pressure. 

Eat a clove of garlic every morning, it dilates your blood vessels and thus helps lower blood pressure. Do light exercises like jogging, sit-ups regularly, don't do heavy weight lifting. Mild exercise produces nitric oxide which also helps dilate blood vessels. Quit foods with high fat content and cholesterol. If you smoke or drink, you better quit it before it's too late.