Beyond this, I find that combat grind occurs when there are no more meaningful choices to be made. As soon as that happens, the whole thing settles into a slog. Once the PCs run out of encounter and daily powers (or expend all the daily powers they're willing to use on this fight), the chances of grind go way up; it is then incumbent on the DM to either end the fight quickly - e.g., the monsters run away - or ensure that there continue to be meaningful choices after the ones built into the system have been exhausted.
Player strategy is a big part of this. 4E is clearly built on the assumption that people will look for the best possible moment to use their encounter and daily powers, even if that means using at-wills for a couple of rounds at the start of the fight. That stretches out the span of time during which there are meaningful choices to be made.
However, a lot of players burn all their encounter powers right away and then have nothing left to do for the rest of the battle. IMO, this is a failure of game design. Tactical mistakes should be punished with defeat, not boredom.
I'm coming to the conclusion that it was a mistake for WotC not to include some way of recharging encounter powers during a fight. IMO, that would do a lot to prevent grinding. (Maybe one standard action to recharge one encounter power?) Or else have some sort of power-up mechanic that keeps people from "going nova" with their encounter powers.