Your forehead and nose are part of the "T-zone" on your face, which is where most people's skin is the most oily. Skin oil production can be caused by a number of things including medical conditions, sun damage, hormones and (the most contributing factor), genetics. Diet has very little effect on oily skin, but exercise does help; sweat keeps skin soft and healthy. After you exercise, however, making sure you wash your face right afterwards because when sweat dries up it can clog pores, leading to blemishes.
Unfortunately, little can be done about your genes and hormones, so the most effective way of keeping you face clean and dry would be to wash you face twice a day gently, then pat dry with a clean, soft towel. Do not wash your face more than twice a day, and make sure your face wash doesn't contain salicylic acid - otherwise you will strip the natural oils from the skin, making oiliness appear later and worse than ever.
I would suggest washing your face every morning and night to start, you can also use toner on your skin to help dry it out a bit. I would also be careful with what make-up you put on your face, stay away from an make-up that is oil based. Bare Essentials is a great natural make-up line that will not add to the oiliness of your skin.
I used to have the worst oily forehead! Always my forehead was shiney and I was so embarrassed! I now use the Citrus Clear Acne Wash daily and it is great at keeping an even skin tone and keeping those fine lines and wrinkles at bay. The product is all natural with no harmful chemicals so my daughter who struggles with acne uses it also and it has kept her acne under control for the last five years. No more oily forehead!!