1. Dilute the spiciness with more non-spicy ingredients.
2. Add dairy (milk, yoghurt, sour cream) or coconut milk.
3. Add Acid (citrus, vinegar, ketchup)
4. Add a sweetener
5. Add a spoonful of nut butter
6. Serve with a bland starchy food (Rice, Pasta, Potatoes)

When I cook for other people, I often sub in paprika/bell peppers for (some of the) chilies/powder, etc