Most of the upkeep on a clothes dryer is simple, and you can do it on a regular schedule. The duct run beyond the cabinet is a different job. Knowing where that line falls keeps the household task small and the professional task clear.
Your part
Empty the lint screen before every load and wash it when it looks coated. Use a brush and a vacuum on the lint housing and the cabinet opening where you can reach them. Check that the exhaust hood flap outdoors opens and closes freely. Look at the connection between the dryer and the wall duct for lint, and notice whether drying times have been getting longer. Write down any change you see.
Before you reach in
For an electric dryer, unplug it or switch off its circuit at the breaker before you move it or open anything beyond the lint screen. For a gas dryer, shut off the gas supply valve before you move it. Do not disconnect or reconnect a gas line yourself.
Hand these to a licensed professional
Call a licensed professional for a long duct run, a run with several bends, or a duct you cannot reach from the outside. Hand off any gas connection work and any electrical work at the outlet or the cord. If the cabinet runs unusually hot, smells of something burning, or the dryer shuts off on its own, stop using it, switch it off, and have it looked at before you run another load.
What to ask the professional
Ask how they will access the full run and whether they clean the duct to the outdoor termination hood. Ask whether they will inspect the connector behind the dryer. Ask what they will record in writing, so the work is documented for the next visit.
Decide by the length and access of the run, not by what you think you can manage. A short, straight, reachable run is a different job from a long run inside a wall. The clothes dryer guide sets out the typical service life and the planning timing for the unit itself, which is a separate question from how the vent is kept clear.