Several commenters have answered this in their own ways. First, you should take some lessons. Better still is lessons plus going on a hosted trip that is centered around spey casting. You'll get instruction and lots of feedback. The instruction will impart a few basic principles you can follow. Second, you need to learn to cast long because you need to cast to where the fish are. Either you wade to them or you cast to them; them's the choices. If you can't cast long enough to reach the fish, it's just casting practice. That's o.k. but you could do that somewhere else at less effort and cost. Third, you need to practice ... on purpose. In most sports, practice is 80% or more of your activity and the actual game is less than 20% often less than 10% of your time. Find a river, pond or even a park lawn where you can practice single speys & other casts - even 30 minutes to an hour. Like any other sport, practice will accelerate your learning. And fourth, if you can, find a partner with whom to practice alongside. Often a partner, even of the same general ability level, can help you diagnose your casting errors. After that, it's just practice and time on the water.