Layout first
Map the stair, windows, support posts, utilities, mechanical equipment, bathroom plumbing, storage needs, and traffic paths before choosing finishes.
Comfort and durability
Below-grade rooms benefit from careful moisture planning, appropriate insulation, good lighting, comfortable temperatures, and flooring selected for basement conditions.
Plan specialty rooms early
Bedrooms, bathrooms, offices, home theaters, gyms, and bars can each create different electrical, plumbing, ventilation, acoustic, storage, or egress needs.