The procedure described below is for a 911SC, but other models are similar.
There may be some minor differences in other year models, but this is how I removed the door panels on my 1983 911SC:
1. Remove door lock button and window sill. The sill is held by two screws, one on each end. The rear screw is under a small plastic plug.
2. Remove the rotary unlocking knob. Pry the cover off the center of the knob and remove the Phillips screw.
3. Disconnect the main door latch. This little linkage is under the door pull handle, and snaps into a small plastic coupling.
4. Gently pry the window switch from the door panel (stiff putty knife works well--be careful not to bend the little metal bezel in the panel that the switch snaps into). Disconnect the wires, after noting which wire connects to which terminal.
5. Remove radio speaker grills.
6. Remove door pockets. There are three machine screws along the bottom edge of each pocket, one sheet-metal screw on each end, and one sheet-metal screw in the center under the pocket lid. Also remove the small plastic door-pocket bracket near the front of the door.
7. Remove the door pull handle. These are held by four allen-head screws, two at the top and two inside holes near the bottom of the handle.
8. Make sure any remaining screws/bolts holding the panel are removed. Then carefully pry the plastic retaining clips loose. Again, a stiff putty knife or scraper works well.
9. This is a good opportunity to inspect the inside of the door to make sure the drain holes are clear, and that there is no rust. Also a good time to lubricate all of the mechanical linkages in the door.