I've posted about npcs several times before but I wanted to zoom in on a particular type that I haven't handled very well in the past: the npc that helps players figure out magic items. If you imagine a game world stripped down to having only one npc, it would probably be one of these.
I can imagine a game that doesn't require figuring out what rings do or how wands work, for example, because players are told immediately upon finding them. The point of the items is for them to feel like rewards, to allow for new abilities, and to provide some fun toys, after all, so why not just streamline towards those ends.
And yet, there is some mystery lost by doing that and some possible fun, tense situations are lost where players have to experiment with potentially dangerous items. So, the compromise is to have a way for low level players to find these things out if they go back to town. Traditionally I've used cantankerous and greedy npcs to do this, but that gets annoying for players fast. And charging too much eats into the idea of the items as rewards (especially keeping in mind that some of these might be single-use).
Another thing to keep in mind is that I'm a ham and like to roleplay a bit to try and make my players laugh. So I want to allow for that without being too annoying. So here is my idea of a new way I might handle this with three different Knowledge NPCs. All of these would be free of charge to talk with, but have some downsides.
"Have I ever told you about the time I . . .?"
Upside: The veteran will tell some ridiculous story that actually has good tactical gaming advice embedded in it. Ever wonder how to teach new players what to do with a potion of diminution or a wand of mineral detection, this old soul can tell them a specific example involving an amusing anecdote.
Downside: The veteran has a poor memory so activation words or potion tastes might be slightly off. For example, he knows a common wand activation word is "something like loose, or lute" when it is actually "luz." The players will have to experiment a bit, but should be able get the right answer without too much trouble.
"Ah, the lay of Phineas mentions such an item, let me sing it for you . . ."
Upside: Get your DM singing and rhyming fun here. A bard type or maybe just a village gossip, this person can help players understand the range of possible items. So, what are the most common ring types in your world? They might reveal a few common types each time. This can help players know what they might want to find or later make themselves.
Downside: Not every story you hear is true. The storyteller will give the truth + some ridiculous baggage. For example, "The wand's activation word is "Luz" but beware, for every time you use it you will shrink 3 inches." The idea is to make the players a little hesitant. The false part can't be too scary though, or they will never want to use it.
"Where exactly did you find this again? I have the memoirs of Helen the Bald in which she describes exactly how she made that item . . . and an indication of her heir."
Upside: The scholar has original sources, or photographic memory of triple-checked accounts and can give you three possible activation words and a recipe for making the device yourself.
Downside: The scholar wants to know where you found this, when, who was involved, all the details. This is a way that any player tomb robbing shenanigans (or thinly veiled lies about such) might spread. It could be a way that rival adventure parties or disgruntled heirs get on the trail of the party. But mostly it will create a bit of worry by implying to players that those are definite possibilities. Also,I think it could still be fun to have a little experimentation involved to discover the actual knowledge. For example, "Helen made three wands of this type, one was said to activate by speaking the word 'Luz,' one with 'Beleuchten,' and one with 'Nur.' With the actual word for this wand being "Luz," but if similar wands are found in the future, the players can try the other two without even consulting the Scholar again.
So, one of these might be more helpful for particular items, for characters of particular level, or even for DMs of different proclivity. One thing you might do is have each of them available nearby and let players alternate and discover the weaknesses of each type. Another idea is, once players are familiar with the npcs throw in a complication, for example the Scholar acts like a Veteran when thoroughly drunk.
But, I'd love to hear details about how you handle this part of DMing in your campaign