G'day
The thing about a large group is that it means that each player only gets a small part of your attention as GM. And if you want to avoid big gaps between characters' moments in the spotlight you have to cut people's slices pretty thin. And that means that you have to deal with everything pretty expeditiously.
My first suggestion is that you make use of the character-players' time in between their turns. For example, you might insist that everybody look up the rules they are about to use in advance, and have their PHB open to the spell they are about to cast, open to the grapple rules if they are about to grapple, etc.
Definitely use a combat grid, which saves people from having to ask about positions, ranges, possible tactics. Also, use a visual display of the intitiative sequence so that people can see that their turn is coming up.
My advice is not to use hordes: it takes too long to declare and adjudicate their actions. My rule of thumb is that the maximum engagement should be one NPC or monster per PC, plus one. And things will zip along better if you rely instead on small numbers of monsters with enough facing for all the mêlée types in the party.
I recommend that you declare what monsters ACs are, perhaps after the first attack on them. That cuts down on the to-an-fro of routine questions while resolving PCs' attacks. Also, use numbered counters for monsters and jot down a key that players can see the shows which are wounded, stunned, armed with different weapons, etc. In short, try to use visual aids to provide all the information that players often ask about at the beginnings of their turns.
Get players to precalculate their total attack bonuses and total damage bonuses with each weapon/attack, and write them down.
Reward prompt decision, declaration, and resolution with a morsel of graphic description. Snub shilly-shallying. If a player says "I'll cover myself from ogre #2 with my shield (that's my Dodge feat bonus) and lunge at Evil Cleric #1 with my magic longsword, hoping to interrupt his casting. I roll a 13, so my total is a 21. That's 9 hit points." reward him with "Your blade pierces his mail on his right flank and draws a spirt of blood. He winces, presses his arm into the wound: and his spell drops."
But if it goes "Is this one of the Ogres?" "Yes" "And this is the wizard, right ?" "No, it's the cleric." "What is he doing?" "Mumbling in Latin and waving his divine focus in a mmenacing fashion." "Okay, I'll bull-rush the ogre." "Bull-rush the ogre?" "No, I'll dodge the ogre. And perform a Golden Wind cross-foot circling fleché to impale the wizard through the groin with my +1 damascus steel antennae-hilted longsword with mother-of-pearl grips. Then he'll have to make a concentration check to cast that spell. I bet it's Spiritual Weapon. [Player shakes his d20 around in his hand for ten wasted seconds] I roll a 13. Plus my AB of 4. And +3 for my Strength of 16. Plus 1 for the sword. Do I get a bonus for the manoeuvre?" "Nope, this isn't Feng Shui, and your manoevre sounds like crap to me." "It's not fair, I haven't studied fencing or martial arts like the others!" "The others aren't getting bonuses either. Your total of 21 hits the cleric's AC of 18." "Okay, I roll 5 points of damage." "Right, five points." "Plus one for the magic sword" "Okay, six points." "Plus three for my strength." "Any advance on nine? Do I hear ten?" "Does he have to make a concentration check?" You ought to snub it with "9 hit points. And he fails his concentration check." Nothing brutal. Just a little positive feedback for saving time.
Regards,
Agback
