Capt Mike Starrett, of Indian Head Charters is a guide on the Potomac who has caught them. Mike posts reports frequently on some other fishing forums. He calls them Potomac Pike!
From his reports, they can be very aggressive, but not always easy to catch, and most he catches are a by catch while fishing for bass. Actually, from what I've read of his reports & those of others, Snakeheads can be as difficult to get to take a fly or lure as bass or any other gamefish we have.
Frogs seem to be the best bet, but they tend to tear up deerhair. Also, they don't appear to be the super predator everyone was concerned about, and don't eat everything in sight. They can be selective apparently.
Some guys have reported seeing a lot them in the Anacostia River, a trib of the Potomac just south of DC. Like bass, they seem to like the shaded areas under vegetation & around piers, and they do protect their off spring even after the eggs hatch, so that could be the best approach as Troutwhisperer has said.
I've not yet had the opportunity to chase them, but I think I would try large streamers & frog patterns.