Lots of good stuff on this thread. Not much to add other than to say a generic pattern that covers a lot of bases is often the way to go, especially in a river. Carp will eat the basic forage available, so a simple buggy pattern is a good bet. I catch 70-80% of my carp on a basic size 10-12 soft hackle pattern. Just a green or black body, bead, and hackle. Bill is right on, they don't chase often (unless their primary forage is baitfish), but if you show them something that looks like forage, they will usually eat it. My go to fly:


Good luck man!