How to DIY it: You should already be emptying the lint trap before every load of laundry. To do a thorough cleaning of the dryer and its vent duct system, unplug the machine (and turn off the gas valve if it has one). Pry off the access panel on the front (try a putty knife covered with duct tape to prevent scratching) and vacuum around the motor and heating element (above). Then carefully disconnect the vent duct tubing from the back of the dryer and use a dryer vent brush (about $10 at home centers; look for one that also cleans refrigerator coils) to pull out any accumulated lint. Aim to do this at least once a year.
How to DIY it: This job can be messy, so protect nearby surfaces by covering them with plastic or cardboard. Spray the springs with garage door lubricant (about $7 at home centers). Don’t use oil, grease, or other lubricants. They may be cheaper, or you may have them on hand already, but they won’t work as well and tend to pick up dust and grit—just what you don’t want on moving parts.