Sanitizer is the most important aspect of your overall maintenance routine and should be tested before using your hot tub or a couple times a week when it's not being used.
The cover should be inspected for damage that would prevent it from keeping heat in and debris, pets, children and critters out.
The water temperature should remain constant between 100˚-104˚F. A drastic fluctuation in temperature could indicate a major problem.
Keep the water line above the hot tub intake or the water won't circulate properly.
A spa vacuum or skimmer is a good idea if there is any noticeable debris on the surface or bottom.
pH, alkalinity and salinity should be tested and kept within recommended ranges as often as possible. If these levels fall out of balance, a hot tub can very quickly become unsafe to use.
Clean the water line and exposed shell with a cloth and hot tub cleaner or vinegar, especially if there is noticeable scum or debris.
Inspect the filter and rinse with water or spray if necessary. A clean filter will help keep your water crystal clear and free or debris.