Sample rate: If you are working at a particular sample rate, for example 44.1kHz or 48kHz, some people assume up-sampling to 96kHz or more is a good idea. Doing so doesn’t gain anything if the entire mix was crafted at 44.1kHz, at least until the mastering stage. If you are working at a higher sample rate when tracking and mixing, by all means, stay up there! Mastering engineers love getting native high-resolution files.