Gion's narrow lanes are residential. Don't block doorways, don't chase maiko for photos, and respect the 'no photos in private alleys' signs.
The city now fines tourists who harass maiko or geiko. Hanami-koji has a strict no-photo policy in side alleys.
The best ethical way to see geisha culture is to book an authentic odori (dance) performance or a chaya tea-house experience through your hotel concierge.