1. For fun. For interaction and sharing with my lady.
2. I plan ahead only so far as when I'm actually buying groceries. Maybe sometimes I'll find a recipe or produce a list of stuff to try. May buy things for 2 or 3 days worth of meals.
3. All sorts of things. From bbq, vegetarian, thai, indian. We both enjoy all sorts of food.
4. No diet really. I prefer vegetarian but we eat most anything.
5. Prep everything before you actually cook. That way you can clean as you go and not be a total tornado train wreck in the kitchen.