The title of the thesis, -Winning Big Customers by Startups- refers to the challenge that small companies face when acquiring large customers. The secondary title refers to a specific situation, where a small company introduces a new product to the market (Self-Service Upholstery Steam Cleaning Device) and faces similar problems when trying to win big customers. The purpose of this thesis is twofold - first, to gain new insights regarding customer acquisition process (with a special emphasis on the big customers), secondly, to develop a marketing strategy for introduction of Self Service Upholstery Steam Cleaning Device into the market. Furthermore, special emphasis was placed on development of a systematic approach to winning big customers within the gas station and car wash industry. The thesis consists of two parts, the theoretical part, where the concept of Customer Development Cycle Methodology (developed by Steve Blank) is explored and the Practical part, where marketing analysis was performed in order to check and confirm the feasibility of the concept of providing upholstery cleaning service in self-service mode. After marketing analysis was performed a step-by-step procedure to approach the big customers was developed. It was concluded that the product has a great chance of success as it provides much better price-to-quality ratio to the end customer than the currently existing cleaning solutions. Moreover, the product provides the customers (gas station / car wash owners) with benefits that are currently not available on the market and besides of a good ROI it can attract more customers to the currently existing services (e.g. end-customers will use this station and not another because of the presence of this device).