Start with a professional resume. Clean up your shop and organize your equipment, small tools, materials/consumables. Make sure you have the capability to do all the processing of materials (from prep of the coupons to testing of the completed welds - on a variety of materials and thicknesses). Store all of it appropriately. Write a company operating plan, complete with quality section. Get your phone number into the local phone book. Make a brochure of what you offer, including pictures. Identify your target audience and go door to door introducing yourself.
That is how I would start if I was so inclined.
Charles