An efficiently-stocked ship's locker contains, at the very least, the following:-
- All the ship's documentation, trading records, copies of the log books (ship's master, purser, trading, engineering, navigation logs), accounts, day books, ledgers, receipts of all trades, sales and purchases, ship copies of passenger ticket stubs, low berth maintenance records, fuel consumption, cargo and passenger manifests, fire and safety records and anything else I can think of) ... it's the future, so assume they're all available in electronic format on data crystals, lots of backups fully synchronised so they're all up to date, with a few traditional "dead tree copies" because of some arcane law that still requires handwritten records
- The weapons locker; all crew weapons, ammunition, weapons maintenance kits all kept in a locker to which the Purser and Captain hold the only keys
- The small equipment storage locker, where items the crew need for missions can be locked away safely, along with maintenance kits and so on. Handheld computers and personal comms stay with the crew: this is for specialised kit such as forensic detection kit, universal translators, handheld intrusion computers for hack jobs and so on.
- The keys to the large equipment storage locker, housed in the spare space on board the ship, possibly near the cargo bay. This is where you'd put larger items such as grav belts, tents and shelters, and so on.
Crewmen keep their uniforms and the kit they need to wear, along with their vacc suits, with them in their quarters. If they're heading into trouble, standard practice is to wear their vacc suits, with gloves and helmets off, at their posts and seal up if it looks like they're about to be exposed to space imminently.
The best policy for Referees is to keep tabs on what equipment and weapons the characters buy, then note their presence in the ship's locker. If the characters need it and they did not buy it, it isn't there for them - so part of the beginning of any adventure should include a list of items that the characters may need to buy before the story begins, whether it be sets of high-tech khaki explorer's uniforms for jungle exploration or high-speed grav chutes optimised for HALO operations.