Not sure if you already see a psych or not, but because I had been already, when the possibility of ADHD came up, I was just asked various questions that my psych didn't already for sure know about me and given a computer test that focuses on quick reaction time and short term memory. It is quite long and boring and very much so on purpose, to test total distractability along with accuracy. My psych looked at my score and the timeline in which I missed or got things wrong, to look for common answer scenarios associated with poor focus and distractability.

I passed with flying colors and do not have ADHD, so don't know for sure if something commonly comes after that, other than the psych preferably getting feedback from one of the patient's close friends or family. (People with ADHD often do not see how severe things are regarding their own ADHD, even if they do recognize it is effecting them, so outside/firsthand observational experiences from a reliable second party are invaluable.) Whenever my fiance feels he needs a quick checkup then again to confirm he is on the right med dose, he also takes that computerized test and gets consistent feedback thusly every time.

I used to work at a medical office, and the same process was used for children and young adults, with children having more school-related questioning (bringing in schoolwork, report cards, and multiple teachers' written evaluations on top of each parent's.) The difference for adults seems to be simply asking the patient's roomate or family member etc., as adults we are mature enough, in theory, to deal with any criticism if seeking help ourselves anyway. Questions about work/college and your relationships therein are also asked.