There are a number of reasons why you may want to participate in a paid psychology research opportunity. First, you might be interested in your own mind and personality, and where you fit on the scales of intelligence, gender bias, attention, emotional intelligence or other metrics. Second, you may have some kind of mental health diagnosis, and none of the current counseling and/or pharmaceutical solutions on the market have given you relief from your ailment. You may want to look for trials to see if you can find something better. Third, you may be looking for ways to supplement your income without taking on the burden of another job. Whatever the reason may be, there are lots of great ways to find trials that you qualify for. Here are some tips on where to look:
Online
One of the easiest places to look is online. You can research lots of different topics in a search engine, and thousands of opportunities will pop up. The biggest issue with this is that, unless you add a city to the search, your nationwide results won't all get you what you want. Many of the research trials require you to visit in person, so it disqualifies many of the sites on a general search. However, by localizing the search results, you can still find hundreds of opportunities in large cities, and a few in smaller cities and college towns.
Radio and Television
Sometimes there are drug trials for psychological drugs in the last stage of approval that seek candidates with certain qualifications. These are usually limited by age, gender, or other factors, and are targeted at getting the group that they have missed studying in initial trials. For some reason, late night TV and radio seem to be the times and places where you are most likely to find the trials you're looking for. Whether this is due to lower priced ad space or targeted demographics is unclear, however.
Universities
Most of the research studies in psychology are either put on by universities or by drug companies. University studies are less likely to be the ones that require drugs, and by contacting the psych department of your local university directly, you are more likely to find paid studies that aren't as well advertised. This might make it more likely for you to be chosen as one of their paid candidates, as an added bonus.
Hospitals
Drug trials for psychological conditions are often run for drug companies through teaching hospitals. If you live near a medical school's hospital, it is a good idea to contact their psych department directly and ask to be put on the list for psych research trials. These don't always pay directly, but sometimes you can get treatment for a condition for free as a result of being in their study.