I've accumulated a horde of stuff but have no way of knowing what things are beyond the very basic description given when you pick it up. How do I ID details about wands, weapons, etc?
If you know Improved Identify, you can cast it. There is apparently one item (though not common) that lets you identify items as well.
Detect Magic will tell you if items are magical, and True Seeing will additionally tell you if the items are cursed.
Otherwise, you need to experiment:
For wands, try using them. That may reveal the effects after one use. (I believe wands do have limited charges, however.)
Potions are often identified after drinking one. Note that, in any given playthrough, all potions with the same description are of the same type. (This also applies to wands and rings.)
For rings, experiment. Some rings have visible effects on your stats. Otherwise, try wearing the ring and seeing if you notice anything different.