This comes up so often it should be stickied to the monster-on-an-index-card blog.
Monsters now do 8 damage + level per attack with at-wills, 75% for AoE and +25% for brutes. Ability scores are used for only two things -- NADs and skill scores -- and have nothing to do with damage anymore.
Do +25 to +50% damage for limited attacks as standard actions (presumably the +25% is when the attack has significant control actions).
A pint of kobold blood drawn by a vampire, a pinch of gnoll hair skinned with the claw of Malar, eye of a gorgon gouged with the handpick of Gond, scales of an orium dragon willingly given, boil and stir in a golden cauldron for 7 consecutive nights leading to a full moon. That should be about the right formula.
or... you could look at the update document, August 2011, Page 39.