The length of your leader and tippet depends on various factors such as fishing conditions and targeted fish species. In general, common leader lengths range from 7.5 to 9 feet, while tippet lengths are typically between 18 inches and 3 feet. It's important to consider water clarity, depth, and speed, as well as the behavior and size of the fish you are targeting when determining the appropriate length. Ultimately, adjusting leader and tippet lengths based on on-stream observations and personal preference will help optimize your fly fishing success.