Empty the trimmed hair out of the housing after every use — a full chamber stops the blade catching properly. Wipe the teeth and plate with a dry cloth. Never rinse the tool, hold it under a tap, or submerge any part of it.
Keep fingers clear of the clamp while it's switched on, and switch off before opening the jaws. Don't use it close to the scalp, and don't use it on anyone else's hair without them being able to see what you're doing.
Charge with the supplied cable only and unplug once it's full rather than leaving it on overnight. Store dry, at room temperature, clamp closed. If the blade dulls, the housing cracks, the cable frays, or the tool behaves oddly while charging, stop using it.