Pull the dryer away from the wall and disconnect the flexible dryer duct from the dryer and the wall vent using a screwdriver. They typically attach with a wire clamp. Turn the connecting screw counterclockwise to loosen the clamp and free the flexible duct.
Insert the crevice attachment on a vacuum cleaner into one end of the hose and vacuum as much lint as you can reach. Repeat the process on the other end of the flexible vent hose.
Vacuum the vent opening on the back of the dryer to remove any loose lint. You may need to use your fingers to pick some of it out.
Remove the grate on the dryer vent outdoors using the screwdriver and wipe all lint off it. Vacuum any lint you can reach in this part of the venting system. Again, you may have to use your fingers to loosen and remove all the lint. Replace the grate.
Reattach the flexible vent hose to the dryer and wall vent using the clamps and a screwdriver.