Better Casting Timing
Several years ago at a casting competition a friend and fellow caster pulled me aside and told me to wait just a bit longer on the backcast. Although I considered myself a reasonably accomplished caster, apparently I was rushing my timing a bit. To my surprise and benefit this helped quite a bit.
This simple bit of advice has come in handy many times since then in casting instruction and guiding. So many times we are so focused on what is happening in front of us that we forget that the most important part of fly casting actually happens behind us. Try pausing just a split second longer on your back cast and you'll be amazed at how many "wind" knots you avoid and on the results of your forward cast. A good way to make sure to do this is to watch your hand instead of your line as you cast and make your hand stop. Your hand is in control so stopping it properly is key. Make sure you don't allow the rod to move too far back or to creep forward before your smooth forward application of power. This can help to avoid tailing loops and is especially important when casting long leaders or dry-dropper rigs.