Also consider attaching a line from your trap to something solid on shore or to an overhanging tree limb.  Just be sure that you have your trap secure enough that it will not be moved by the current or by the fish inside it, or you could easily come back empty handed without a fish OR a trap.  Next, consider the area you want to fish.  If you are fishing warm weather, you will want to place your traps with the entrance facing down stream, in shallow, rapidly moving water.  

Focus on areas where there are trenches or sudden drop offs.  The mouths of tributaries are another good location for your traps.  Concentrate on areas where there is cover.  

Catfish are somewhat lazy hunters.  They will find areas where current will carry unsuspecting prey past them, and lie in wait, taking advantage of the situation, to swim out and nab their dinner as it floats past.  They are motivated by smell, though, so if you can put your trap in an area where they are likely to be lying about waiting for dinner, and tempt them with the scent of something they find inviting, they are much more likely to investigate.  If you are fishing colder weather, again concentrate on the areas where there are rapids and cover, but concentrate on the deeper areas where the fish will seek refuge in deep beds where they hole up conserving their energy.  Once more, put the mouth of your trap facing down stream.

As the catfish moves up the stream, the specially designed funnel shaped trap opening allows the catfish to swim in, but they can not turn and swim out.

To get the full "How To Use Catfish Traps" article you'll need to download it here.