Use your Performance Chart, a tool I've developed, to illustrate your growth, achievement, and depth of contribution. This chart should be very detailed on all the new job duties and responsibilities you've taken on that warrant a step up in pay. Prepare a persuasive pitch. Role-play your request. Identify any objections you think your boss is likely to make and prepare solid answers.
Timing is critical to success.
Be sure to pick a time when your boss is likely to be receptive and more positive, adjusting your request to fit the boss's personality and operational style. Remain positive throughout the encounter. Don't push it if there's no immediate response. And if the answer is no, ask exactly what is required to get a raise. You may have hit a ceiling as to what this particular job is worth to your employer.