If it's a cheaper bass (like my Squiers), I throw a set of Hipshot tuners that match the originals on it, sometimes install a D-tuner if the spirit moves me in place of the E-string tuner, install a Hipshot KickAss bridge, copper foil or use shielding paint in the electronics cavities, and maybe add a thumbrest if it doesn't mess up the pickguard. So far I've been OK with the stock pickups on the Squiers (though I did install a Seymour Duncan Antiquity II in a Jay Turser TeleBass copy that I bought over 10 years ago). Jazz basses get a push-pull pot installed for series/parallel circuitry. If the neck turns out to be funky I have it worked over by the Guitar Doctor in Reading, PA. The better basses get a D-tuner, and if I get really fussy I will replace the stock tuners with Hipshots to match the D-tuner's brand. I keep all of the original parts, and if I decide to buy another bass--with my current practice of when one moves into my collection another has to move out--I reinstall the original parts on the departing bass and recycle the good parts on the new member of the family. All of my basses get Dunlop Dual strap locks installed and new strings too.