On my engine (0-320 D2J), the oil pick-up screen is located near the bottom on the aft side of the sump. From the outside, it looks like a safety wired bolt screwed into the back of the sump. To remove it, you clip the safety wire holding it in place, then unscrew the fitting, which is 5/8" or larger if I recall correctly. By the way, you'll want to do this AFTER draining the sump.
Once you get it fully unscrewed, the threaded portion pulls out and brings a tubular screen with it. I place the entire assembly on some white paper towels to drain, then look down into the screen through the open end to see if there is any debris. In addition, you can simply pull the screen out of the female socket that is in the threaded plug. If you find debris, it is time to play junior scientist and figure out what the debris is. I've never found anything other than a few flakes of engine crankcase sealant.
Once you clean the screen and slide the tubular screen back into the female socket, you can screw the entire assembly (don't forget to use a new copper sealing washer between the plug and sump) back into the sump, re-safety wire it, and you're ready to go other than adding oil and whatever other tasks remain from the oil change...
