How to monitor the use of Nootropics?
The process of measuring the effect of nootropics would be the same as for any other drug: Do a double blinded placebo study and the follow the parameters you hope to influence. For example do "brain tests" if you want to test for enhanced brain function. If there is any function of your drug in the body, you will see a difference between the treatment and the control group. You could start by reading the Wikipedia article about Nootropics which is quite exhausting and also has quite a lot of references and go on with these two papers "Does taking vitamin, mineral and fatty acid supplements prevent cognitive decline? A systematic review of randomized controlled trials." and "Cognition enhancers between treating and doping the mind."