Additional recommendations I've heard :
- Skip Darkening for leveling.
- I wouldn't chase the bounties for the +exp set either. Wait until 70 when you have a little more of a full build/mobility. Side trip in story mode for Crown of Leoric is fine though if you don't get one while leveling.
- The high-density zones are a slightly faster alternative to rifting. You have to maintain a massacre bonus though and it can get painfully boring.
This guide is a good place to start that covers most of the bases.
Edit: the one thing it doesn't cover is doing the Challenge Rift before starting season and getting the headstart with level 1 gambling.
Diablo 3 S16 | Leveling Guide for ANY CLASS (Tips, FAQ) 2.6.4 | Team BRG