If my HDL is low what can I do to help bring it up?

Lifestyle measures. The best way to raise cardioprotective HDL is cardiovascular exercise. Shoot for forty or forty-five minutes daily. Supplementation with no-flush Niacin may help as well, 2000 to 3000mg daily in divided doses. Fish oil supplements may help this as well, as healthy fats can raise the HDL.
Carnitine/niacin. Carnitine can raise HDL and lower triglycerides, Niacin will raise HDL and lower ldl.
Exercise +. Cranberry juice has been shown to increase HDL levels. Fish and other foods containing omega-3 fatty acids can also increase HDL levels. In postmenopausal women (but not, apparently, in men or pre-menopausal women) calcium supplementation can increase HDL levels.Aerobic exercise. Lose weight. Stop smoking. Avoid trans fats. Drink alcoholic bev. In moderation.Increase monosaturated fats.
Diet and exercise. Some non-medicine ways to raise HDL include daily cardiovascular exercise for at least 30 minutes, replacing saturated fats with unsaturated fats and limiting red wine consumption to one glass per day. Additionally, there are medications (over the counter and prescription) that can also raise the hdl. Consult with your doctor for specifics.
Exercise and diet. Hdl is usually increased by exercise. Also try to increase Niacin in your diet or take a Niacin supplement over the counter. It can cause hot flashes and flushing in some folks. If that doesn't work for you, there are prescriptions your doctor can write that may.
Exercise. Hdl is best raised with exercise. Of course a healthy diet and weight loss if applicable help. Niacin which comes as a prescription formulation as well helps, but start with exercise.
Excercise. Exercise exercise exercise. Some meds help a bit too. Do not forget diet also.