I also let my PCs roll an initiative for their team versus the initiative for my monsters. I agree, this way it will force the players to create tactics and teamplay.
I also make my battles dynamic. Attack rolls vs Defense rolls. As stated earlier, you just subtract the flat 10 in defenses. So defense stats will look like this.
AC: +7
Fort: +4
Ref: +7
Will: +2
I also added critical effects to make the game more random and fun.
If ever they roll a natural 20, excluding the full damage, they will also roll d%. and compare it to a char of effects.
D%: Critical
95-100 Knocked unconscious or stunned
90-94 bleeding (ongoing 5 damage)
76-80 weakened
66-70 crippled (slowed)
56-60 dazed
46-50 blinded (-5 attack)
31-40 Knocked prone
20-26 immobilized
1-10 normal damage
If they also roll a natural 1. Not only they will grant combat advantage to all enemies until the end of the PCs next turn. They will roll a d% for effects too.
D%: Fumble
95-100 Full Damage self
88-94 Half Damage self
75-80 Reroll attack
51-70 Knocked prone
31-40 Disarmed (1d8 direction; 1d6 distance)
21-25 Sundered
1-10 Attack ally (dice depending on number of allies)
Then if ever they rolled a natural 20 or 1 in defense rolls, the effects are just simple but really nice.
Perfect Block [20]: the defender can make a free action melee or range basic attack against his attacker.
Fumbled Block [1]: the defender grants combat advantage to his next attacker
Another little but nice house rule. if you push or slide a creature against a wall, you have +1d4 bonus dmg.
Giving my rogue PC access to Improved Feint feat. Feinting is now a minor action instead of standard.
and I borrowed from Dragon Age, if ever PCs faint or in other words, reaches 0hp or below as long he is not dead, whenever he comes back into consciousness, he rolls a d% and compare it to a chart of negative effects. These effects are cumulative per faint. and they cannot be removed until they reach extended rest.