To build a four-season room on a deck, gather materials like treated lumber, insulated windows, and composite roofing. Install lighting fixtures and consider HVAC systems for climate control. Essential tools include saws, drills, and measuring tapes, while safety gear like gloves and glasses is crucial. Ensure adherence to NAHB codes and standards, and consider hiring professionals for electrical and HVAC work. Plan for building permits, warranties, and maintenance guidelines to ensure safety and longevity.