The Celtics need more easy offense. When Rondo and Ray Allen are getting down the floor and finishing and/or getting fouled, the Celtics' whole game starts clicking. When they slow down and go halfcourt for extended periods the offense really bogs down.
It guess it starts on the defensive end. They need to regain their defensive intensity to get steals/turnovers/rebounds and get out on the break. They should also try running more after made baskets (a la D'Antoni) when the other team is making an offensive run.
To be blunt, I find the C's halfcourt offense to be rather tedious and, at times, just ugly. But when Rondo is flying down the court and dishing to open guys, the team is beautiful and exciting to watch. Oh, and more effective too!