What is the best way to approach retailers to get your product on their store shelves?

By demonstrating their is strong demand for your products. Best also to go via distributors rather than individual stores. Remember to get on a shelf something else has to be removed. Are you looking to replace an existing product? If yes does yours carry a higher profit margin than the current one? What makes you think it will sell more? The harsh reality is that the bigger brands have wide product portfolios which equates to stronger distribution. One off product producers have only a tiny chance of succeeding unless the product is unique, in big demand, and not offered by the bigger players. That said no harm dropping stock off at a local store and asking the store owner to pay in a few months. They can then assess demand levels - if it sells well they will order more, if not they have not borne the risk and can return the unsold stock. Either way you get rich data to decide the next steps.