When it comes to merit increases, your boss has discretion about how much she gives you, so long as the average raise she gives doesn't exceed a certain target, say 3.5 percent. So she might award the top performer 5 percent, but below-average employees only 2 percent.

But there might be more money available than your manager lets on.

Smart companies "always have a little something in their back pocket ... to use when they need it - say to keep an employee they can't afford to lose," said Dallas-based compensation consultant Rebecca Elkins.

Say you fit that category, and you request an 8 percent raise when the company typically has offered you 4.5 percent.

Smart managers would ask themselves, "Am I willing to lose this person for $500 a month?" Minneapolis-based compensation consultant Jim Fox said. "If they're concerned about losing you, that extra money is minuscule, pennies compared to what it will cost to replace you."

What you should do: The day of your review is not the time to negotiate a higher raise since your manager has already gotten approval for the increase he's budgeted. Your campaigning should start months before. "You have to sell yourself all year round. Don't be shy about telling your manager, 'Hey, I did this,'" Elkins said.