If your hairline is receding and it is due to Male Pattern Baldness, this is what I suggest you do.
If you have Male Pattern Baldness, there is a good chance that you will start thinning up top.
Get Propecia (finasteride) and rogaine 5% (Minoxidil) and Nizoral (Ketoconazole) shampoo.
I'd suggest getting the Nizoral 1% shampoo (the 2% is somewhat harsh from what I have read and the 1% is just as effective).
Take the Propecia everyday (get a prescription from your derm or order it online).
Apply Rogaine 5%(Minoxidil) to the areas that are thinning or you want to grow back.
Use Nizoral 1% 2-3 times per week. Make sure that you leave it on for at least five minutes before rinsing.
If you just want to maintain, you could just start off with the Propecia.
If you want to save money, get Proscar and cut it in 4ths, and take it daily instead of Propecia.