I have two hourglasses. One one minute, and one 30 seconds.
Everyone new is on the *one minute timer. If you go out of time, your character automatically take the dodge action (total defence in some other games or whatever is closest to that.) I assure you that slow thinker starts to think faster. And it prevents the check cell phone syndrome. Players follow the game much more closely than without the time constrain.
If I see that a lot are taking just a bit less than a minute, I jump to the 30 seconds timer. Now things goes real fast. With six players we talk about a round that lasts 4-5 minutes tops, including my moves!
(Note: I am allowed 1 minute per groups of foes composing the opfor during a fight, 3 types of foes, 3 x 1 minutes for the DM or otherwise, my NPCs will take the same dodge action as the players).
Also...
I cast X spell... roll to hit/save and damage at the same time if single target. This means that the player rolls the save of his/her target. This speed up the play even more. Rolling to hit, then damage or then the save slows the game. Players still roll their own saves (they like to roll and it's half the fun
) and I often use averages for filler monsters but for tougher foes, or "elite" I roll damage. This make my rounds quite fast. Try it.
*Warning: The first time you will introduce the "timer/hourglasses" be ready for an uproar. But as time will go on, your players will love it and even ask for it whenever a newer player comes in and takes a wee bit too much time. A rookie (a rare thing in my groups) is allowed a one minute timer but after a few games when he gets the hang of the game, he is down to the 30 second timer too.