Reminding your boss about a promised raise is a delicate issue. You want the raise, but you don't want to create any awkward feelings in your working relationship. Clear and upfront communication about the raise helps prevent headaches later on.
Get It in Writing
Verbal commitments to a raise are easily forgotten and often not strong commitments. You're in better shape to issue a reminder if you have a commitment in writing. Even an email in which your boss detailed the steps necessary for you to get the raise is helpful. When you have a written promise, you can share it at the time you remind the boss. If not, your best option is to outline what you have contributed to the company since the promise was made.
What to Say
If you have an email documenting a commitment, forward that and alert the boss that you are sharing a friendly reminder about the raise. If not, ask for a meeting. Note the raise with something like, "Three months ago, we talked about a possible raise. You mentioned at that time, that we could take a look at my progress at this point and adjust my salary by 5 percent if I met my goals." The next step is to support what you accomplished verbally and with supporting documentation. You might say, "During the last three months, I have increased my customer satisfaction score to 97.8 percent. This rate is well above the target we set of 95 percent."