Hi Mate,
The likely looking areas already mentioned are good places to start to locate river carp, especially any permanent boat moorings.
River carp can be somewhat nomadic in their travels but they are also creatures of habit. In my experience, most populations of river carp have a 'home' that will return to after their travels. If you are lucky enough to spot a carp in a stretch, that area is definately worth targeting. If you happen to see a feeding carp, then get a rig in there!