Apple's fingerprint sensor, Touch ID, isn't flawless for everyone. If you find yourself having to rescan your finger more often than you like, this workaround might help.
Photo by Janitors
Apple gives you five fingerprint slots for Touch ID. Instead of enrolling five different fingers for each slot, enrol one of them multiple times. Timothy Stenovec on the Huffington Post says:
I thought that having more — and more varied — prints of my thumb could only help, so I tried it by "enrolling," as Apple calls it, my thumb two more times. The result was fantastic — Touch ID now works much better than it did before, probably over 90 per cent of the time.
Combine this with the trick to register more than one finger in each slot, and you might be able to improve your chances of the fingerprint reader working every time.
This Quick Trick Can Vastly Improve The iPhone's Fingerprint Scanner [The Huffington Post]