So, here's how to negotiate from a position of power. These tips come from Money magazine:

• First, information is everything. So, compare your salary to others doing the same job. You can get estimates from websites like Salary .com. Or ask headhunters about current rates.
• Then, figure out how much your company values you. After your last review. What did you do to correct any problems or weaknesses? If you're just plodding along, doing the same ol' same ol', don't expect a bigger check. Quantify your accomplishments. Like, today you oversee 10 sales people, while last year you managed 2. Or maybe you found a way to streamline the organization. It's important to show how you make a difference.
• Also, when you ask for a raise, you need a fallback position. So, ask for 15% more than you really want. Or have an offer for a better-paying job. Just don't start out the negotiations by threatening to leave   it'll put your boss on the defensive. But there are other things beside money that are valuable. Maybe you could get more time off, or work at home once a week.
• Next, find out when yearly budgets are set, and schedule your meeting about 10 weeks before that. Keep in mind, most companies do their budget planning in the Fall. Or ask for your raise after you accomplish something big, when your boss is pleased with you.
• Finally, once you get in there to talk about your raise, listen more than you talk! And don't be afraid of silence - it often forces people to talk, making it more likely they'll back down, revise their position, or tell you something useful.

If you'd like to go further, check out the book Getting to Yes: Negotiating Agreement Without Giving In by Roger Fisher.