I am a new smoker and have made a couple of simple modifications to my Char-Griller Model #2121.
First, I reversed the wheels. The manufacturer recommends they be placed on the left end of the frame which results in having to pick up the smoker by the fire box to roll it. This struck as a completely idiotic design choice, so I turned the frame around allowing me to roll it around by picking it up by the shelf.
Second I replaced the thin, cedar planks used for both shelves with some 1x4 kiln-dried, pressure treated boards I had left over from another project. I added a leaf/shelf to give me a little more room to place food trays.
Easy to do and now much easier to use the smoker.