How do I make predictions about future sales and expenses in order to create a cash flow projection?

Research your industry, look for trends you may be able to take advantage of, look at the past, figure out what you might do differently going forward, look at details, test the market, look at your social media presence. Be the most informed person possible on the subject of your business. Your SBDC consultant can help with the process. Keep your notes because if you apply for funding your banker may want to know how you came up with specific numbers.