Practice makes perfect
No matter how good a caster you are or how long you have been doing it, or how often you fish there is always something to learn and room for improvement. Out on the water is the perfect place to practice, rather than on some patch of grass somewhere. Practice a cast you don't use very often, the roll cast is one that I don't use that often and when the time comes that it is necessary I always wish I was better at it. Mending is another part of the cast that can always be improved on. Specialty casts such as a serpentine cast a series of "esses" put into the line to aid with a drag free drift, a steeple cast ( a high back cast to avoid bushes etc.), and the aforementioned roll cast are examples of casts that most of us could use practice at. So the next time fishing is slow take the opportunity to practice because as they say practice makes perfect.