There are many ways to increase your blood pressure, like eating fast food, but in the same time you don't want kill yourself. Eating fast food will raise your blood pressure levels but it will raise your cholesterol
levels, which can lead to heart attack
, and makes you fat as a start. Salt is also not good so I would say you may drink come coffee to raise your blood pressure. Some coffee so not much, try to exercise (if you don't have heart issues or other health issues).
If nothing has worked for you then might need a medication to put your blood pressure in normal ranges.