Honestly, the best stuff is 100% DEET, but use it sparingly, mostly if you are planning on bushwacking, and be sure not to wash your face or put your hands in the river, and don't wear it if you are swamping. It will wash off into the water, and we don't want that, Jeff, do we?
(sorry, in an ornery mood...)
Most of the time I use permethrin. Spray it on your clothes outdoors while you aren't wearing them, let them dry two hours. Don't spray it on your body! It lasts for several weeks. Then remove the clothing immediately, put them into garbage bags and tie them until you wear them again. I generally wash mine immediately instead but the permethrin (aka permanone) doesn't last as long that way. Shower immediately. And tuck your pants inside your socks! Forget shorts. And in hot weather, consider the supplex pants, you can get them at Dicks or LL Bean or online. They are worth every penny. They dry in minutes, and keep you cooler in warm weather than jeans. Consider gaiters too. I just recently got some and love them.
I have noticed that when I am wearing my hip waders (rubber) that I get substantially fewer ticks, too.
Renee