There are several things you can do to slow down hair loss. If what you have is male (female) pattern baldness, then it's in your genes, can't stop it, but, again, you can slow it down.
Balance diet and exercise helps out because it keeps your body in shape to ward off other ailments. But for hair loss, consider minoxidil, Nioxin, Hairobics, etc.
Watch this Dateline NBC video. It'll give you some ideas. It studied 5 treatments on 5 different men over 1 year.
I also created a website to share my experience and help others. There might be some ideas there for you as well.