Measure the inside of your door frame. Purchase adhesive foam rubber weather stripping based on the length and width of your door frame.
Clean the inside of your door frame with a cloth, warm water and dish soap to remove dust or grim on the door frame that will interfere with the adhesive on the stripping.
Peel away the paper and attach the stripping to the inside of your door frame. Press the adhesive side against the frame. The stripping will provide cushion for the door as it shuts. This will prevent the door from slamming loudly.
Check to see if your door is attached to a door closer. A door closer is a jointed arm attachment that will be attached to the door and door frame on either the outside or inside of the door. If the door is regulated by a closer, but it still slams, you need to adjust the closer.
Use a screwdriver to adjust the door’s spring tension. Turn the spring tension screw at the top of the door closer's long, thin cylinder. Turn the screw clockwise for one full rotation.
Test the door. If the door is still latching too quickly, turn the screw again. Continue testing the door and adjusting the screw until the door closes and latches at the desired speed.
Use a level to determine if the door and the door frame are level. If either is off, the door won't stay open and the door will continually slam shut.
Purchase a kick-down door stop to prop the door open. Use a drill and screws to install the door stop on the lower outside corner of the door on the side where the door latches.
Move the arm of the door stop into a downward position when you want to prop the door open. When you want the door to shut, move the arm of the door stop upward. The door stop will have a rubber cap at the end which will keep the door from slamming shut when the stop is in the downward position.