If you have a hookah at home, cleaning makes the biggest difference to the taste. Change the water every time and rinse the base: old water smells and spoils the next session.
Every few uses, brush the stem in warm water and wash the bowl. A little lemon juice or baking soda removes stubborn residue; avoid soap, which can leave a taste behind.
Hoses are the hardest part. Washable silicone hoses can be rinsed and dried, but old leather ones can't and are better replaced. Only light coals and smoke in a well-ventilated room, never in a closed space.