Select an online IQ test. You might try the Mensa workout or IQTest.com (see Resources). Note that not all online IQ tests abide by any particular standard and will vary in length and format.
Do not use any additional aids, such as pen and paper or a calculator. Mental problem solving is key to any IQ test.
Work quickly through the problems. While not all online IQ tests are timed, those that are may factor the time it takes to complete the test into your score.
Submit your IQ test. Self-scoring online IQ tests will present your score on the next page. Note that some may charge you to see a "complete report." Use your discretion.
Remember that most online IQ tests are for entertainment purposes only. High IQ societies such as Mensa require that you take a test in person. Check with the specific organization for details.