Re: Improving my cast
To improve your casting, get some casting lessons. To improve your fishing, get a guide or an accomplished fly fisher to teach you by taking you out fishing. This fishing trip should be to assess all your fishing skills.
Some of the time inadequate casting skills are the result of choosing the wrong spot from which to cast, and what cast to make. By not knowing the best place from which to cast, or the easiest cast to make, you can make your presentation more difficult.
In Gary Borger's book Presentation, he defines presentation as everything that goes into catching a fish. This includes reading water, choice of fly, type of leader, choosing your casting position, sneaking up on the fish, choice of cast, etc, etc.
The reason I mention this is that you mentioned "presentation" as one your goals. Becoming a better caster is one step. Part of becoming a better caster is not just distance and accuracy. I think learning what cast to make: curves, mends, puddle casts, parachute casts, off side casts, elliptical casts, water tension casts, tuck casts, and a combination of the previous casts with a mend. And when to use these casts is really one of the way you can tell a really good fly fisher.
The more options you have for the types of casts you can make, the easier the fishing becomes. A basic straight line cast is only the starting point. To use a baseball analogy, you are concentrating on being able to hit a faster fast ball by concentrating on casting a straight line cast farther and more accurately. When the fish throws you a curve, a slider, a change up, etc; you need to be able to hit those as well.
Or to add onto what the last poster said, Tiger Woods does not just practice hitting a driver. He also practices hitting out of bunkers, and heavy grass. He practices backspin. he practices reading the green. He practices putting uphill, downhill and along a slant. Think about adding more shots (casts) as well as improving a straight line cast.
"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy