The International Door Association recommends inspecting and testing your garage door and garage door opener monthly.
To test the reversing safety feature, completely open the door. Place a 1 1/2" thick piece of wood on the floor in the center of the door opening. Press the button to operate the door. If functioning properly, the door should reverse automatically.
Also visually inspect springs, cables, rollers and other door hardware. Do not attempt to adjust garage door springs -- they are under very high tension and could cause injury if not handled properly. If they appear to be worn, call a professional. Consult your owner's manual for recommendations on lubricating door and opener parts.