In a world heavily dominated by social media and digital content, anyone can make a preemptive decision about you without ever meeting you. You want to make sure that what is being shared online does not hurt your image or affect your professional brand.
Keep your head straight.
Tilting your head makes you look less confident.
You should be the only subject.
No group photos with others, pets, or objects.
Your face should be clear in focus.
Make sure the image is not blurry.
Use a recent photo of yourself.
Do not mislead others with an old picture.
Wear appropriate attire.
Wear something that you would wear to work.
Use a photo of you smiling.
Nothing too serious or unpleasant.
Always use a real photo.
Do not use any default or "silhouette" images.
Source: HRCap Guidebook