I`ve a couple of routines, as below, but when starting up just to warm up have a few exercises I run through.
First routine is if just keeping my hand in so to speak then I just play along to fave songs on Youtube.
Second is if for a gig, as we don`t rehearse that much I`ll get the set list and play through it a few times on the week of the gig.
Practice set-up is whichever bass into an Ampeg SCRDI into an Mini Ashdown Stack, which only has one 1x10 cab connected. I don`t practice at anything above normal watching TV volumes, but I`ve put some foam underneath the cab to hopefully isolate it a tad from the floor.