Setting goals and expectations is key to having success, and good football coaches know how to set the bar for their team and then hold them to that standard.
Whether it be with grades, discipline or play on the field, a good coach can see the potential that individual players, and his team as a whole, possess, and he doesn't relent until they meet and exceed that potential.
Accountability about expectations between a coach and his players is a huge factor in whether or not a team is a unit. When everyone is on the same page, it's much easier to succeed. It also helps keep players out of trouble, as they know what lines they just can't cross.
Being clear about those expectations is also very important. You can't be expected to meet a goal if you weren't told what it is, so a coach that can clearly communicate with his team regarding what he wants to see from them and what they need to accomplish is huge.
This is also a huge motivating factor when it comes to working in the offseason or at practice.
When expectations are high, great coaches will not settle for anything less, and they will prepare their team to meet the challenge.