AKA, Playing with a Real Drummer
This is probably blindingly obvious to most of you, but it wasn’t until I started playing with a real drummer than I started paying attention to drum cues.
I had always played to drum loops or a metronome, and my timekeeping is pretty darn good at this point. But I had never realized that those fills were signals to the rest of the band.
I hope that when @JoshFossgreen has a chance to do a “How to Play With a Drummer” intensive lesson, that this will be one of the bullet points.
It wasn’t until I started playing bass with my garage band that I figured out that the snare roll or big double hit on the crash cymbal meant, “hey, dumbass, we’re going to the 3rd verse now.”
It is a godsend when you can’t remember whether you’re on the 15th or 16th bar of the repetitive guitar solo to hear a big tom fill that signals the start of the outro.
If you haven’t before, start listening for those cues.
Josh actually does have a lesson like that in the course IIRC… I forget how deep it is, but there’s an entire module about jamming with the band I think? Been a couple years…
He does, but there’s been some talk of a more detailed lesson with a real drummer in the room and them going back and forth about how to play with a drummer and the drummer’s perspective on locking with the bass player. That is one I’m very much looking forward to.
And I genuinely hope when that happens that the drummer points out that those fills aren’t just flash, they are cues that alert the rest of the band that they’re coming up on the next section of the song.
Bingo!
I haven’t played with a drummer, but will attest. Whenever I’m learning a song, I crank up the drum track from the original song and follow the drummer just like you said. It really helps a lot listening for cues.
I also use the cues from the vocalist.
As someone who has been a singer in several bands before taking up the bass, I can attest that sometimes those bass fills or turnarounds as you transition between sections are also key signals to the rest of the band.
I would also welcome a tutorial from @JoshFossgreen with a live drummer about how to work together.
Bass and drums, two peas in a pod. I’ve been very lucky, all but one I played with were good drummers and we stayed out of each other’s way when it comes to fills. He’s great with giving a wrap up little fills 4 bars before the end of the song so we know when it’s coming.
It’s exhausting when playing with drummers who doesn’t know where she/he is in the song and/or can’t keep time.
That’s what’s so great about the Blues 
And pray pray pray that the drummer knows the song better than anyone else on stage. This little bit from Pat Metheny says it all!
(essentially - the drummer on the bandstand is running the band whether you want it / or they know it or not)
As talented as each member of the Beatles was, and as good of songwriters Paul and John were, they were going nowhere until Ringo joined the group, and then they took off. Paul has stated this publicly.
So true! Ringo is a special kind of genius, not very flashy but drum parts he laid down on those tracks fit the songs perfectly.
So true and another reason the Bassist has to lock in with the Drummer but try and tell a lead guitarist this. 
Acid jazz on the fly
Videos at rumble of real time song writing jam, Tell me what you see
John Layne and the Aeon’s Promise band
To me the bass is the power in the band, bass moves the mood, the drummer and bass must be in sync however folks see that, Jaco pastorious to country slow walk, bass links the rhythm and melody. Thats its job to a songwriter…
But it can also.be a driver of the songs feel and dynamics…
There are places where simplicity is required, and places for the bass player to dream and lay out where the song is going…
John