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Turn Management
Monsters never stop spawning and your stomach never stops churning. Identifying absolutely everything is not a good strategy, especially when resources are lacking.
"What if I missed something good?"
There is always the fear that you might have missed an item. But this game is not designed to obsess over an equipment that might or might not be more useful than your current gear. Read up on speed-runs to think about how little other players have ascended with.
Even with Bags of Holding, weight is a serious issue. It isn't worth lugging everything around the dungeon to identify it. If you cannot identify it conveniently, leave it as is or stash it away and come back to it later if you still need a better gear later. After all, you may find something very nice in the future. Remember, stash, stash, stash. Don't lug everything with you.
Item Rewards : Always
Certain areas, monsters, and events come with particular loot that is always worth identifying. Consult the wikis for more info.
Cursed Items : Sometimes
It is only worth the time to carry around and identify a cursed item if you know what it is already and still want it. Which means uncursing it first.
Amulets : Always
Amulets are rare and can be quite valuable.
Unusual Items : Always
Some item types don't show up very often, so when they do, it's worth investigating. For example, snow boots, gloves, capes, tools, etc.
Weapons : Rarely
You don't want to spread your #enhance points thinly, so you generally only want to take the time to identify items of the class you wish to major in.
Armor: Sometimes
Nethack randomly generates loot, so even though you just killed 25 Uruk-Hai and they all appear to have dropped the same cloaks, short swords, iron shows, orcish bows, and shields, they are not the same at all. There may very well be an enchanted item in there.
You should check it if:
it wasn't typical monster loot
it's reasonable that this armor might have a higher enchantment, or provide better AC
the item might have an extrinsic attribute
Potions : Beginning-game: Rarely Mid-game: Always
If you have many of a same type of potion, its likely to be a healing potion, but other than that, it's just too risky. Smoky and milky potions could contain a djinn, so it may be better to save them until you can bless them for better chances of a wish. Other potions will be identified gradually as they're thrown at you. Generally serious potion'ing begins once you've obtained a unicorn horn mid-game.
Scrolls : Beginning-game: Never Mid-game: Always
Any desirable permanent effects from scrolls are generally better used mid-game when your inventory becomes more stable and less fluctuating. Except for scrolls of identification, which will generally be the most plentiful.
Wands: Always
If you know a wand is uncursed, it is always worth the time to identify it
with an Elbereth engraving.
Wands can very well be a "Wand of Nothing", so wands that cannot be identified as above are usually more situational and less useful to be carrying around - stash those. Remember that there are some wands you do not want to put in containers.
Rings: Always
If you can BUC test a ring, and know it is uncursed, always try it on. Beginning-game, if it doesn't immediately identify it's likely situational and not worth wearing due to the hunger penalty.
Spellbooks: Beginning-game: Sometimes Mid-game: Always
Beginning-game, there's little room for vast stat improvement. If you're a class with low intelligence, its more likely you'll cause the spellbook to crumble upon reading attempts, netting nothing but wasted turns. If you have an unsuccessful read, it's very likely the next attempt will also be unsuccessful, so stash for later.
Gems: Rarely
Most gems you pick up will be garbage. They take up weight and inventory slots and don't sell for much. Generally they're only worth hauling around for unicorns or shop-keepers.
Tools: Always
Tools auto-identify. If you know it's not cursed, try it out to find out which version of the tool it is.
