Here are some tips to help you get the best possible Face Recognition results:
1. Use a large, good quality photo. Good photos are typically larger than 100KB. But if your Internet connection is not very fast, avoid huge photos that are several megabytes large.
2. Photos from webcams and mobile phones are sometimes not of sufficient quality for Face Recognition. If no faces were found in the photo you uploaded, try using a better quality photo taken with a digital camera (or use a scanned printed photo).
3. The face or faces in your photo should be frontal, i.e., facing the camera. Faces appearing in profile will not be detected. The face or faces in your photo should also be straight. Faces at an angle skew the results and make Face Recognition less accurate.
4. The faces in your photo should be fairly large, so it is best to use a photo featuring one person or a few, rather than a group photo with 10-20 people in it, where each face is rather small. Note that's it's fine to have more than one face in the photo, Face Recognition will run on every face that was detected.