It comes down to the type of person you are dealing with really but the most pragmatic approach would be to indicate that you feel you deserve an increase but are stuggling to quantify how much as your perception of your worth to the company won't be as accurate as theirs. At that point ask them to suggest a figure. Give them the opportunity to take time away from the discussion to think about it.

The only negative about putting the ball in their court is that it gives them control of the negotiation as they can easily come back with an extremely low figure stating that they have discussed all of the options with the appropriate personel and the quoted figure is their absolute maximum allowable increase, leaving you with zero scope to stretch it.