Years back in one of our earliest fly fishing forums, a few fly anglers and myself did a lot of cussing and discussing knots used in fly fishing to the point one, Bill Nash even wrote a book on the subject. In short we found that one must beware of leader and tippet claims by manufacturers as at times these may be off a tad in diameter and lbs test.
Other neat things that came out of those discussions were that knots for Flourocarbon, Mono and Braid are not created equal and what's great for one might not be the greatest for another. One other tip is that to avoid friction and heat from destroying your knot before you start fishing, moisten it well before pulling it tight. A great moisturizer is lip balm and is better than saliva and today you can get it with sun screen and protect your lips and knots.
Many common knots such as the clinch knot are very poor as they lose a lot of the strength of your tippet, etc.
Knots that scored high were and are the Trilene Clinch, the Pitzen, and the Uni-knot for connecting fly to tippet as all scored near 98% using mono.
The common Clinch Knot for instance, scores just 65%. In other words if the tippet you are using tests at 5 lb test, using a clinch would reduce that to around
3.25 lbs test and will likely cost you fish.
I've noticed of late that a fair fishing show on tv called the North American Fisherman has the Berkley Knot Wars as part of it's programming. This will give you great heads up on the various knots and how they test out against each other in the search for that perfect knot.
Learn to tie your knots the same each time, test your knots against each other using short sections of mono with hooks tied in each end using various knots. Always moisten, and as an old Chief MSgt told me once "Pay attention to Detail!"
With that said there's always more to learn and I for one would love to hear from you with your tips you've found helpful in solving Knotty Problems! Knots are at the center of our sport, from tying the fly on to tying tippet to leader, building leaders, tieing the leader to the fly fline, the fly line to backing and the backing to the arbor so let's hear from you?