First thing I would do is a bit of research and find a good location that has the potential of producing some keepers, maybe a park or campground located on the river or an old swimming hole that is no longer popular. Be ready to dig some junk on the shore. If you plan to get wet, do even more research. Find out what the laws are in your state regarding salvage. Some states believe that everything in the rivers belongs to them and if you are caught with a metal detector in the river without the correct salvage permit, jail time and big fines. I would look into a small creek or stream or maybe a lake swim beach as they are usually not considered navigable streams and therefore not under any governmental control. Now that that's out of the way, you will need a waterproof detector (why take a chance with your land rig)a good scoop, a mesh pouch for trash and treasure and a good spot. If you have a swimming hole picked out that has a nice shallow spot, work it first. This is where the mothers and dads will go to play with the wee ones and there's a chance their rings will fall off playing with the kids. Look for rope swings. Plenty of goodies under them, but that might require diving.
OK, I've got to get back to work now. Shoot some more questions and maybe we can get more people involved here