How do I stop my armpits from sweating?

I have really bad armpit sweat. It doesnt stink because I use Old Spice Odor Blocker Body Wash, but I always get pit stains in my shirts. It is nasty and I always have to wear black. Most of my friends get pit stains but not as much as me. Like mine are really bad. How do I keep my armpits from sweating?