The above mentioned you tube recommendations are great sources of quality instruction for tiers that have some experience but if you can find a hands on beginners class, take it. The learning curve will be flattened out and you will learn about proportion and material management. That's hard stuff to learn from a video, sometimes. There are some invaluable books out there that provide more than just instruction, they give you perspective and an understanding on the how and why of a given fly's developement which is something that is becoming lost on some of today's modern tying phenoms. A cool looking fly is one thing, a cool fly that will catch fish is another matter entirely.