To define your target group for social media: 1. Understand your product and customers' needs by learning how your product is used and what drives purchases. Create buyer personas to represent your ideal customers. 2. Gather customer data and use analytics tools on social media platforms to perform market segmentation. 3. Evaluate your competitors' strategies on social media to see what works best and adapt it for your own use. 4. Test your social media strategy on your target market and fine-tune your campaign based on results.