Asking for a raise is like making any sort of business recommendation. You want to prepare effectively, and present arguments and documentation that show how you help the company.

Why Do You Deserve a Raise?
Be ready to explain why you deserve a raise. There could be several reasons:
Your job has changed. You're doing more work than you were hired to do, or you're doing a different job altogether.

You've saved the company money. Perhaps you renegotiated a contract with a vendor on terms more favorable to your organization. Or maybe you've developed your skills so that you do your job faster than your peers.

Your labor is worth more on the open market than you're being paid. If you quit, you could find better-paying work elsewhere.
You haven't received a raise in more than a year, and inflation has reduced the value of your pay.
You may deserve a raise because of a combination of these factors. In any case, consider why a raise is justified from the company's perspective-it will help your manager justify paying you more.

Prepare Documentation
Once you've determined that you deserve a raise, prepare documentation that shows exactly what you've done that merits more pay. If your job has changed, show what new responsibilities you've taken on. If you've been doing excellent work, write down the goals of your projects, and next to the goals, how you exceeded them.

Keeping an ongoing project list can help you remember what you've done, when you did it, and the results. Refer to old e-mail, calendars, and any other places you've written down your accomplishments.

Managers want to reward high-performing individuals, but are sometimes too busy to track their progress. If you can show how you've exceeded expectations, you can show why you deserve a raise.

Know What You Should Make
Once you've documented your contributions, research the going rate for your position in your industry. Trade magazines, websites, and salary tools are the best places to learn what others are paying. Providing this information helps your manager make your case with the HR department, executive team, and others who sign off on raises.

Do a Trial Run
Before asking for a raise, try your arguments out on a friend. Also, consider objections your manager might bring up, and think about how you should respond. Remember to tie your answers to how you've helped the organization. Those who help their companies succeed are usually the ones most deserving of raises.