The answer is easier than you might think: Just be straightforward.
For instance, your wording might sound like this:
"I was hoping that we could talk about my salary. It's been a year since my last raise, and in that time, I've taken on quite a few new responsibilities. I'm now solely responsible for overseeing our website and, as you mentioned last week, our results in that area have shot way up. I've also been managing Jane since Carlos left, and I've been able to resolve the concerns we'd had about her relations with vendors; that area has been going really smoothly since I began working with her. In addition, I know you're happy with the changes that I've made to our press releases, and we've been getting a 25 percent higher rate of response when we pitch those. Now that I've been doing these things for a while, I'd like to discuss increasing my salary to a level that reflects these increased contributions."
Note a few key points about this language:
* It doesn't just say that you'd like more money, but lays out reasons for why the raise is deserved. By explaining how you've been contributing at a higher level than when your salary was last set, you can make the case for your compensation to be raised accordingly.
* It references work that you've already done, not work that you're promising to do in the future. Some people want to ask for a raise as soon as they take on new responsibilities. While this can make sense if those new responsibilities are part of a promotion to an entirely new job, if they're simply a new part of your existing job, it's generally more effective to wait until you show how well you've done with the new tasks. "Pay me more to take on new work" generally doesn't go over well, outside of a promotion. But "I've taken on new work and here are the outstanding results that I obtained in doing so" is often precisely the formula that will garner a raise.
* It makes a case based on your value to your employer. There's no mention here of what your co-workers get, or the fact that you need more because your kid is about to go to college. It's all about why your value to the company has increased, and why your compensation should reflect that.
Aside from preparing yourself with language similar to the above, there's also one more thing that you should prepare before walking into your boss's office to make that raise request: what to say if the answer is no.
Too many people just skulk off feeling dejected if their raise request is turned down. Don't let that be you. Instead, be prepared to say something like,"What would it take for me to earn a raise in the future?" A good manager should be willing to talk with you about specifically what you'd need to do to hear "yes" next time.
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the co-author of Managing to Change the World: The Nonprofit Manager's Guide to Getting Results, and former chief of staff of a successful nonprofit organization, where she oversaw day-to-day staff management, hiring, firing, and employee development.