First, knots. Knots can be the bane of any fisherman. There are so many that each fly-fisherman needs to know, even before he ties his fly on to the tippet. Once he gets to that point there are numerous ways to attach a fly to tippet, from the classic Turtle (Turle) Knot to the newer Davy Knot. It's important that each fly-fisherman knows the knots for every part of their rig.
First, to connect the backing to the reel comes the Arbor Knot, then the backing connects to the fly line with an Albright Knot, to connect the fly line and leader together most use a perfection loop but the classic Nail Knot is still used, but what happens when we need to tie new tippet to the leader, the Blood Knot or Surgeon's Knot is used, now we have to connect the fly to the tippet, there’s the Improved Clinch Knot, the Turtle Knot, or the Davy Knot. That’s a lot of knot work just to get a fly on the water.
One thing that should be pointed out about this commandment is the word "thy" in "know THY knots." This is not a call to know every single knot in the compendium of knots, no, this is a call to know the knots that you use. If you use the Surgeon's knot to combine leader and tippet material then there is no reason to familiarize yourself with the Blood Knot, likewise, if you use the Davy Knot to connect a fly to tippet, don't worry about knowing how to tie the Turtle Knot. When you're first learning knots you should try to learn each knot, that way you will know which knots you prefer and which knots are easier for you to tie along the river. Once you've made that decision, practice those knots
Rods, reels, and line aren't our only set of gear though. Some people go to the river with nothing more than that and a small fly box in their pocket, others go into it with pockets full of "necessary" gear. And to them it may all be necessary. But, each fisherman is required to check their gear and make sure that it is "artfully" rigged. If you carry rolls of tippet for just in case, make sure that there is tippet on the spool before heading to the river.
Also, make sure that everything you carry has a purpose. If you're going out for trout on a small creek where the monsters are going to be 14" long, you probably don’t need to be carrying that "Gurgler" fly. That's not to say that the lunker couldn't take that large, surface Bass fly, but it's incredibly, very unlikely. Now, there are some fly-fishermen that want to carry their entire fly-fishing arsenal in their vests, and that's completely alright. But go through the gear every now and again. If it's been a while since you last opened that one pocket you might find a fly box that you thought you misplaced. Also, if you have a fly box that "suddenly" disappeared, how bad did you need the flies in that box. Sometimes it's good to de-clutter.
"The Curtis Creek Manifesto" First Commandment continues to be relevant for us today. As always, Good Luck and Guid Luck!