The Social Contract is the implicit or explicit agreement between people to behave in a certain way.
I want to propose some explicit conventions for the 4e social contract for combat situations, not because there's a problem with any players I game with, but because in the middle of the Heroic tier, 4e slows down. Then it slows down again in mid-Paragon, and then even more at the start of Epic.
The reason it slows down is that you get more and more options every round, and your actions start to impact the other PCs more and more. So not only do players spend more time thinking about their choices, risks, and trade-offs, they also start thinking about the other players' choices, risks and trade-offs. That's fun (if it wasn't Pandemic would have been a flop), but it's also easy to lose perspective. 97% of the time, the PCs win, and the fights are just a part of the story.
Here are three conventions you can propose to your players for social behavior in 4e combat...
1. Be Ready. Try to choose your action when your turn is about to come up. Feel free to pre-roll so you can focus on story instead of stats. It lets you do more verbal/creative than dice/arithmetic during your turn. Compare! "I pivot around his shield and swing at his knee with my mace, 22 vs AC for 19 damage." Versus, "I think I'll use Mace Attack. That's +10 vs AC... I rolled a 12... so 22? OK. It does 1d8+11. And... I rolled an 8, so... 19 damage."2. Live and Let Die. When it comes to the other players, please let them screw up. Let them screw things up for your character, too. Respond in character to their mistakes if you must. Talk about it OOC as a side conversation after their turn or after the combat. I call this one "live and let die," because there may come a time when a player makes an almost-good-enough decision when his character's life is on the line and you'll have to bite your tongue. Or shout "Noooooooooo!" in character as the monster makes that OA they didn't consider and drops them like a sack of potatoes. If saying "live and let die" seems too harsh, replace it with "let it ride" or some other colloquial phrase (gambling jargon is full of good ones).3. Keep it IC. Table talk about tactics and strategy must be done IC. That means that the enemy can hear you. Out of character side talk is totally OK as long it's not with the person whose turn it is, and we don't have to talk over you. (This is a game, not a board meeting.) Feel free to ask rules questions of other players before your turn.
These are more "ideals" or "goals" than rules with sanctions. Because you're adults. But also because you're adults, you can talk about social expectations and actually make stuff better. You're saying "this is how our ideal combat goes, even though it doesn't always actually go that way."
The titles of each convention are short imperative phrases to make it easy for your group to communicate them.