Taking another note from military science, it is important for a player to know the difference between strategy and tactics ("All men can see these tactics whereby I conquer, but what none can see is the strategy out of which victory is evolved” - Sun Tzu). Tactics can generally be regarded as the activities or patterns used to execute a strategy. Strategy, on the other hand, is the big-picture plan.
For example, let's assume that you are getting ready to step on the court for a big match. You have done your practices and workouts according to plan. You have analyzed your environment and have read your opponent. You are almost ready. Before you start, you should consider developing some sort of big picture plan for how the match will unfold. For example, should you be aggressive or defensive. Should you give the opponent pace, spin, height or angles. Etc. This is the basic road-map that you attempt to follow throughout the match and it constitutes your overall strategy. Your tactics, however, are a bit more refined. By being aggressive do you mean to serve-and-volley or charge the net off the bat or do you want to work the point before you "belt-and-bolt". If the strategy is to pick on your opponent's backhand, do you do so by first moving him to the forehand, or do you plan to merely serve hard or kick-serves to it.
In other words, having a game-plan is not necessarily enough. It's important for a player to have a subset of plays or patterns which are to be used in executing the game plan. As the quote above indicates, the player should be kept in the dark as to the overall strategy because you will implement it via multiple plays. Although, in her mind, she's thinking that you're doing X you are really doing Y. But, of course, in order for this concept to work, you need to have the appropriate weapons. You can be the best strategist and tactician in the world, but if you're fighting with bows and arrows and the opponent is launching cruise missiles, then you're, moist likely, not going to win. That's why we stress that you should practice EVERYTHING. Develop ALL parts of the game..all weapons, so that you can combine these aspects to maximum effect.