The mechanical elements of a garage door need to be constantly maintained and serviced otherwise repairs may become more frequent or costly. Dusting and cleaning the motor boxes and other mechanical elements is a good tip for self-maintenance. A professional must do large-scale garage door repairs as the machinery is complex and the door heavy and cumbersome.
A more old-fashioned style of garage door is the tip-up type. This is when the door swings upwards and outwards and does not follow an elaborate track mechanism. A system of springs and pulleys makes up this system and it can be automated. The springs on this systems are heavy duty and tightly wound, only a profession (with aid) can remove, adapt or fix these springs. They are highly dangerous to change and maneuver during repairs or service. The choice of springs is based on how often the garage door will open and close; the more amount of time that the garage needs to move, the stronger the springs need to be.
Sectional overhead mechanisms pull up the garage door so that it lies parallel to the garage floor. The roll-up mechanisms literally roll up the sheets of metal that are the garage doors. The sectional overhead mechanism and roll-up mechanism also contain springs and wheels that need to be kept well lubricated and clean. These are more advanced systems than the tip-up garage doors and it is best to call a repairman when they have problems. 
When the automated garage door motor becomes faulty then it is best to call in a repairman as soon as problem. Most garage door installers and manufacturers also offer warranties on these mechanical boxes. Garage door installers also can supply replacement parts and accessories, as you require them.
The standard procedure for repairs is to either call the dealer or manufacturer who installed the garage door in the first place. If this is not possible then it is best to get at least three quotes before deciding on who will be best to help you. Repairs may be costly but a garage door is an investment for your home and your property.