Fingerprint on iPhone and iPad

How to make Touch ID better at recognising your fingerprint on the iPhone and iPad devices

It's really simple - since iOS allows you to register multiple fingers, what you do is register the same finger multiple times. By doing this you can press your finger (or thumb) on the sensor in different ways so it gets registers from a variety of angles.
Another thing you can do is since dirty of damp fingers fail to pass muster with Touch ID because it sees them differently to clear, dry fingerprints, you can also register a finger when it's damp (not soggy or wet) and dirty.
This can be a real timesaver if you have sweaty fingers or operate your iPhone or iPad with dirty hands.

Touch ID & Passcode

To do this click on Settings and go to Touch ID & Passcode . You'll be prompted to enter your PIN or passcode and from there you can add more fingerprints by clicking Add a Fingerprint.
You can add as many prints as you want, and you can give each enrolled fingerprint a unique name (which might come in handy for fine-tuning this trick).