I finally gave my common back to the lfs a few weeks ago. I bought a large net first, since I needed one anyway... think it was 8" wide.
The pleco was in his usuall corner, and I placed the net in the water covering the way I thought he would go. Then I took my long grabber and placed in the water and came up on him to get him to swim away. He swam right into the net and stopped (I didnt spook him or anything, just enough to get him to move). I slowly brought up the net and he didnt even thrash. I re-used a large bag that I had just got from the lfs when I bought some plants. Guess I got lucky it was so easy, especially with my heavily planted tank. The only thrashing he did was when I had him in the net in the bag and trying to dump in out of the net. Good luck with yours.