Make a project checklist, with the budget at the top and target time lines for major work such as emptying the garage, installing new lights and drywall, and finishing floors. List each part of the project, including renting a temporary driveway storage unit, inspecting doors, electric outlets and switches, and boxing up and labeling garage contents to store during the work.
Remove everything from the garage, discard broken and trash items, donate unwanted items, and box up and move all other items into the temporary driveway storage unit.
Thoroughly clean the space by sweeping the floor, vacuuming walls and ceilings, and washing any grime off floors, walls, trim and outlets.
Inspect all electrical outlets and switches, light fixtures and electrical sources. Call an electrician if necessary to ensure the electricity is in safe working condition.
Remove any broken light fixtures, switches and outlets, and replace them. Install new, larger lighting to match the design you have planned.
Inspect all walls, the ceiling and the overhead garage door. Replace any broken or cracked drywall, installing insulation if desired. Weatherproof the overhead door and insert insulation in panels.
Paint the walls and ceiling a light color.
Patch any cracks or expansion joints in the cement floor if necessary. Seal the cement floor and paint it.
Install workspace counters and storage cabinets on at least one wall -- more if desired.