Craft a legal waiver with your lawyer that states the test subjects are aware of the potential dangers of the experiment and will not attempt to sue you or anyone else in the experiment if they experience ill effects from taking the ginkgo. These side effects may include headache, nausea, gastrointestinal upset, diarrhea, dizziness or allergic skin reactions.
Screen your potential test subjects to find out who is allergic to ginkgo, who takes anticoagulant drugs, which subjects have bleeding disorders and if any have scheduled surgery or dental procedures. Remove subjects that meet these criteria.
Let the subjects understand the test procedure. Half of the subjects will be given ginkgo and half will be given a placebo. Randomly choose which subjects will receive each, but don't inform any subject.
Place each subject one at a time and show them a series of memory cards. Time how quickly they match the cards from memory and write their time down on a sheet of paper. Perform this act with each subject.
Give each of your subjects a week's worth of supplements. Make sure you know which subjects have received the ginkgo and which have received the placebo. Instruct them to take their supplements daily but to keep their normal eating and exercise habits otherwise.
Gather the subjects together after the week has passed. Perform the same memory test with each subject, writing each of their times down after each test.
Find out how the subjects' performance changed after the week. Find out if the ginkgo test subjects performed better than the placebo test subjects.
Repeat the experiment with new subjects. Use the exact same methods for a second time. Perform the experiment several times to get a wide range of test subjects.
Average the performance change in the ginkgo subjects and the placebo subjects, and note whether there is a drastic difference in the two.