This Best Practice Guide is a companion piece to the Unite Unity Europe 2016 talk Optimizing Mobile Applications. It covers much of the same material, but with supplementary material added for the interested reader. You can watch the talk itself on YouTube: Unite 2016: Optimizing Mobile Applications.
While the Unite talk implied that the covered topics might only be relevant to mobile performance, much of the talk was applicable to a general audience. Effort has been taken in this write-up to discuss information related to performance in a broad and platform-independent manner.