Step 1: Check the remote for information.
Inspect the old remote, if you still have it, for a model number and brand name. In some cases, this information may be inside the battery housing or on the reverse side of the battery cover.
Step 2: Write down make and model information.
Check the garage door opener's motor housing -- the large box typically hung on the ceiling where the garage door rests when it is open -- for a label indicating the manufacturer and model number. Some brands may also list a manufacturing date. Write down any pertinent information you find on both the remote and the motor housing.
Step 3: Contact the manufacturer or local retailer.
Call the manufacturer's customer service number to order a new remote or find out which type of replacement remote is best for your opener model. If you purchased the opener from a local garage door installation company, they most likely know which remotes work with your opener -- and they may be able to sell you a new remote.
Programming the New Remote
Step 1: Add batteries to the remote.
Place the appropriate batteries into the new remote, if necessary. Many remotes have the batteries pre-installed. You may have to pull out a protective tab to activate the batteries.
Step 2: Ready the motor unit.
Climb a stable stepladder and press the button on the opener's motor housing that says "learn code" or a similar phrase. The motor unit should then show a flashing light or make a sound.
Step 3: Press the remote button.
Climb down from the ladder and move at least 5 feet from the motor housing unit. Press the "open" button on the remote unit within 30 seconds to program the motor housing unit. If you have a three-button remote, choose whichever button you prefer to open the door. Look for a light or listen for a sound to indicate that the motor housing recognizes the remote.
Step 4: Test the remote.
Push the remote's "open" button to ensure the device is working properly. If nothing happens, repeat the programming process, beginning with pressing the button on the motor housing unit.