For a startup, the best growth strategy is usually to focus on product-market fit and acquiring users through word-of-mouth. Once you have a strong user base, you can experiment with other growth channels such as paid acquisition or marketing.
For a larger company, the best growth strategy will vary depending on the business. However, most large companies will need to focus on organic growth (growing revenues from current customers) and inorganic growth (acquiring new customers through mergers and acquisitions).