If you think should be paid more for the work you're doing right now, forget all this incessant whining about "the bad economy," do your homework. Start by doing some salary survey research online at the Bureau of Labor Statistics (www.bls.com). Then gather together any recent performance appraisals you may have received about the job you're doing and any other information that you think is relevant to your worth as an employee. Find out what, if anything, your employee manual says about compensation policies.
Bear in mind your employer may genuinely be limited by budget constraints. If, as is very likely in your conversations about a raise, your employer responds with concerns about the budget, ask whether there is a time of year when the budget would compensation increases. Know what you want and be prepared to justify the increase you're asking for. At the same time, be flexible. An employer may offer a couple extra weeks of vacation in lieu of a salary raise. I once had a job (back before everything was so "bad" with the economy) where I regularly got additional time off instead of a pay raise. Eventually I had eight weeks off per year.
Once you've set up a time to meet to discuss salary, present your request clearly, rationally, and calmly. Don't ask for or expect an answer on the spot. Nothing of value can happen that quickly when it comes to pay increases.
Remember, that even when you're completely deserving of more and you've presented your case persuasively and professionally, your employer really may not have room in the budget for a salary increase or other adjustment your compensation package. Also, your employer may be fully justified in not wanting to create inequities by adjusting one employee's compensation without adjusting everyone's. But that doesn't have to be the outcome in your case, and regardless of what you think will happen or what state "the economy" is in, you most definitely will not get a raise if you don't ask for one. You may decide that your job is worth keeping in any event, but no one's going to ask for a raise on your behalf, so go do it. Expect the best and be prepared for the worst, as they say.