Use a red-eye reduction feature on your camera or phone
Increase room lighting before taking the photo
Avoid direct flash by angling the camera slightly
Ask the subject to look at a bright light before the shot
Take photos from a different angle
Use a larger light source instead of a direct flash
Edit the photo with red-eye removal tools in photo software
Manually correct the eyes with a healing or brush tool
Use glasses with anti-reflective coating for future photos
Replace harsh flash with softer lighting when possible