Curse-testing

In many cases, you want to test whether or not items are cursed. Here are a bunch of ways to do that, though this list is likely incomplete.

Ways that work on all items
These methods work for all classes of object.

Altar testing
Items dropped on an altar will glow black if cursed. You must not be blind to use this technique. (Blessed items will flash blue.) This is a common method later in the game; even in Gehennom you can use the altar in Orcustown. Sometimes you want to figure out cursed status before you can get to an altar; other methods can help with that.

Pet testing
A pet will "move only reluctantly" over any stack of objects that contains one or more cursed objects, as long as the pet was not whistled onto the stack (using a magic whistle) and the stack contains no food. Pets will greedily eat up food of their preferred types without regard to cursed items underneath or above the food.

Identify
Reading a scroll of identify (or casting the spell, or getting the gift from a throne) will reveal the cursed status of any items identified. If you can cast identify at low failure rates and want to know the status of something now, this can actually be very useful.

Wield the item
Wield the object you want to identify and try to unwield it. If you can, it wasn't cursed. This method has the problem that, if it was cursed, your hands are now wielded to the object. This is fine if you have a scroll of remove curse you were looking to burn or can cast remove curse at low failure rates --- as long as the object wasn't a two-handed weapon.

Try to make a monster wield it
Drop the weapon in front of a monster that will pick it up and wield it. If the weapon "welds itself to the monster's hands" or something similar, it's cursed.

Throw projectiles
Cursed projectile weapons like darts, daggers, or shuriken may sometimes veer wildly off in another direction if you or a monster tries to throw them. They will not weld to your hands if you do this. You can #name a cursed projectile and other cursed projectiles of the same enchantment will stack with it, allowing you to detect further cursed items.