When I first read the thread heading I assumed it meant things you did with the bass that you did/didn't worry about. Throwing your bass up in the air and (hopefully) catching it, using it as a pry bar to open the lift gate of the pickup truck after a gig or as an emergency substitute badminton racquet... Relieved to have misunderstood. Anyhoo, aside from the obvious pitfall avoidance regarding hopelessly warped or bowed necks, frozen truss rods, butchered/hacked "mods" and other horrors, first priorities include playability and comfort. Without that you won't get to the point of letting the bass become a musical conduit instead of an appliance. That includes neck size, profile and finish. Next is the resonance, sustain and lack of any dead spots. Again, can't do much with those, either. Third consideration is sound. "What? On a musical instrument? How can that be?" you may ask. Mods. You can always get a comfy instrument to sound good but you can't always get a great sounding instrument to feel comfortable. Next would be aesthetics. If it's hideous, I'm not attracted to it; if I'm not attracted to it, I can't play my best on it; if I can't play my best on it, I don't want it. What's the point? Things that don't matter is the name on the headstock, the overall condition (within reason, see above), cleanliness (a little dust and rust never hurt nobody), year and country of manufacture. This is especially true with newer instruments. In the '60's some of the firewood imported here masquerading as basses was awful. By the '70's it got better, today you have to actually read where it was made to know.