Topical minoxidil (pic related) should be your go to. I can attest that it absolutely works for reversing the "bald spot" hair loss pattern at the top of your head. However, I heard that it isn't as effective at reversing receding hairlines, and that you need to take the pill form for that. The only real side effect that I have experienced from topical minoxidil is having an itchy scalp sometimes.