When buying a genuine leather jacket, focus on the quality of the leather, stitching, and overall craftsmanship. Full-grain leather is the most durable and ages beautifully. Check for smooth, even stitching, as this indicates good construction. Ensure the hardware, such as zippers and buttons, is sturdy and functional. The fit should be comfortable, allowing for movement without being too loose or tight. Lastly, buy from reputable sellers to guarantee the jacket is truly genuine leather, as lower-quality imitations can mimic the appearance but lack durability and feel.