Find the location of the stick. Open and shut the door, observing the top and bottom as you do. Locate the area that is sticking.
Clean out the area behind and under the door. Dirt can build up on thresholds and in between the door and the frame. Use a small broom to clean this out or if necessary, a degreasing cleaner and a sponge. Wipe the area clean. You can also use a putty knife to help scrape away any stubborn dirt.
Use silicone lubricant spray. Use a can of silicone lubricant and spray down the hinges, and the top and bottom of the door. Hold the can about six inches away from the door. Make sure the wind is not blowing in your direction while you do this.
Tighten any weatherstripping. Underneath the door and attached to the frame, weatherstripping can also cause a door to stick. Tighten down the threshold weatherstripping with a screwdriver and push in any side weatherstripping with the side of a chisel to flatten it.