Dry out your tent after every trip
No matter how dry you think your tent is at the end of your trip, it’s always worth letting it hang for 24 hours in your house when you get home. Moisture can linger in strange corners of your tent, and it will soon create that unmistakable and hard to vanquish “moldy tent smell” if you don’t dry it out completely.
Never wash your tent in a washing machine, the agitator can damage it. Try handwashing with gentle soap in a bathtub, and air drying outside.
Read more detailed tent cleaning tips here.
This tip is from "1001 Climbing Tips" by Andy Kirkpatrick