Lubricating: 
Do NOT use WD-40.  It's a degreaser.
Use lithium based grease.
Lubricate all moving parts.
Rollers - Plastic need to be replaced every couple of years.
       Ball bearing metal - Use tube with grease spray to get into ball bearings.
       They probably need to be replaced every
       Sealed (nylon) - Don't need to do anything.
Don't grease track.
Springs:
   Extension springs on each side that stretch - No maintenance.
   Torsion springs - Wind up around rod.  Grease the spring.      

Chain Drive - lubricate top where mechanism slides. Don't lubricate bottom.
Screw Drive - Lubricate once or twice a year. With thicker lithium grease.