When I was diagnosed as an undergrad, my doctor titrated my dose.
This is basically running a self-study on yourself at a dose for 2-3 weeks (work for stimulants, not the ones that take 4-6 weeks to build blood levels like Strattera). Then, you do incremental increases (5mg, 10mg, 15mg, 20mg, etc.) and keep track of productivity and side-effects.
For me, I did 5-20mg of Ritalin. Each increase made me more productive, but, after three days at 20mg, I felt a little dizzy and like my heart was racing. I called my doctor, and 15mg was my best dose at the time.