Retaining Good Employees Question:

You have to get compensation right, as best you can, all the time. These days, anyone good is going to get a raise to move and may be a signing bonus on top of that.
The thing is--you can't counter. It's too late by that point. Once they tell you they have another offer they're already out the door. A raise won't do it at this point, at least not for the good ones.