How do you get a child tested for adhd?

ADHD. You can request your child's school to perform a psycho-educational evaluation. This will greatly help the pediatrician in making the diagnosis in addition to vanderbilt screening.
Thru your doctor. Psychologists, psychiatrists, pediatricians in my community.
Ask pediatrician. There are two avenues for evaluation. Start with asking for a 'CORE' evaluation in school. During the evaluation, there will be testing that shoudl be helpful in making the diagnosis. Speak to your pediatrician about your concerns. You may get a referral to a neurologist or psychiatrist who can help with the diagnosis and management.
A good clinician. Start with an experienced well trained professional.A thorough physical exam, medical , family, mental history and clinical observation.Symptom checklists are helpful but limiting.Comprehensive scales such as the basc-2, cbrs and others help identifiy comorbidities, cpt help assess whether symptoms are typical of adhd or non clinical group.Qeegs arecostly, but could be helpful.Psy/ed assessments help.