Columbia Academy in East Hanover, I explained the five considerations occupying my mind while I play a game of chess, in descending order of importance: 1) pawn center; 2) tempos; 3) material; 4) initiative; 5) piece coordination. In other words, I will sacrifice a small amount of material, usually a pawn, if I can obtain the better center and/or a lead in development.
Even though you can't see a tempo, think of each tempo like a pawn. There is a risk involved when you sacrifice material: you must use every tempo wisely. Otherwise you have insufficient compensation, meaning that you are down a pawn with nothing to show for it.
Of the five considerations mentioned above, the most difficult to understand for beginners is piece coordination. Chess has been described as a non-verbal language. If true, then piece coordination is really no more difficult than speaking a sentence in which the parts of speech agree with one another. Positional blunders are the equivalent of bad grammar.
The class concluded with a practical session. Students were given a homework assignment involving three different tactics: double attack, pin, and fork.