One of the most useful but often overlooked steps in mixing is choosing an appropriate mix to reference.
Remember that old adage: "Nothing happens in a vacuum?" Well it rings true in music as well, and certainly as it pertains to mixing music.
If you've ever tried to mix a song you've likely been there at some point: "Why doesn't my mix sound like such-and-such?" Well... were you referencing such-and-such when you were mixing? Want your mix to sound like Beyoncé? You better damn well be listening to and REFERENCING some Beyoncé!
Referencing doesn't mean passive listening while you go about your day, or on your drive to the grocery store. Referencing means active listening and returning to listen again and again. You have to put in some work. It takes time to find the right song that has a similar vibe to the song you're working on, or has a particular quality that you want to emulate in your mix.
You may be asking yourself, "so what am I listening for?" It could be any number of things. Maybe the balance completely changes in the bridge and you want to do something similar, maybe the type of delay used on the lead vocal in the chorus is your jam! The important part is that you're listening, recognizing a sonic idea, and judging whether or not that idea will work in the context of the song that you're working on.
When I'm referencing mixes in my mixing process I always import the song(s) I'm referencing into the Pro Tools session I'm working in. This makes quick A/B comparisons possible, and keeps me honest about the effectiveness of my efforts.