I'm currently creating my first completely homebrew campaign and I'm planning on using the the DMG treasure tables (p.136 - 149) to generate treasure in my campaign.

I want the world to feel organic and alive outside of their campaign - rather than just created for their exact needs. So rolling treasure randomly really appeals to me. That way the items they find won't always be obviously suited for one party member specifically, or maybe for any party member at all. While some rolled items will be exactly what the party need/want others may prompt difficult decisions about who would benefit most from using them or
whether they should simply be sold for coin or traded away for potions.

Most of the rolls on the treasure tables generate specific items, however, there a number of items that are a bit vaguer:

• Ammunition, +1, +2, or +3


• Armour, +1, +2, or +3


• Spell scrolls (cantrip or levelled spell)


• Weapon, +1, +2, or +3

None of these rolls refer to specific items. When I roll any of these items on the treasure tables, how should I decide what to assign to my party?

Is there any official guidance that I've missed? Have any other tables been published that I can roll on to assign these things randomly (i.e. a table that includes all weapon types - if I've rolled a weapon, or all 2nd level spells - if I've rolled a second level spell scroll).

If there isn't anything like this, then what techniques for assigning these sorts of items have you found to work well in your own game?

Taking +X Weapons, as an example. I don't want to only hand the party weapons that they're predisposed to using but I also don't want everything I give them to be useless. There also shouldn't be a completely flat distribution of weapon types - in any typical fantasy world you'd expect to find more magic daggers and shortswords than flails or tridents. Just making the decision myself about what they find, however, feels quite arbitrary.

It is trivial to simply roll on the weapon or armour tables in the equipment section of the Player's Handbook.

As a note, you say that you don't want flat distribution, e.g. that you would expect more daggers and shortswords than flails or tridents. But bear in mind that the weapons, armour and items you find on a monster or in its treasure hoard are not, in universe, going to be completely random! For example, the lair of a sahuagin tribe are far more likely to have tridents and nets than daggers! In a meta-sense, treasure is no more likely to be random as to be what a DM decides is likely to be found for a particular area or monster type.

I don't think the rules suggest specific items like that, outside of the Magic Item tables A-I in the DMG

Therefore, exactly which +1 weapons the party find is down to you. As DM, I usually give the party magical weapons that match the sorts of weapons they tend to use, but you may feel as though the world is too tailored towards them, rather than feeling like the world is something that exists outside of them and their adventures.

Randomise it

In this case, I'd suggest adding a random element. Assuming you are DMing for a party of 4, I'd say roll a d100 to decide on a percentage of whether it'll be suited to one of them or not, then roll a d4 to decide who it's for (if the d100 said "tailor it to the party"), or roll a dX to decide a random "common weapon" like a dagger or a shortsword (if the d100 said "don't tailor it to the party").

This way, if you can't decide whether to give the barbarian who uses a greataxe a +1 greataxe or whether to give a +1 dagger because that's more likely to exist in your world, you can use the dice to make that decision for you. And, as always with random methods like these, if you find you don't like what the dice just told you, overrule them.

_{Note that my answer focuses on weapons, but that's just to pick an example. This can be used for armour, ammo, scrolls, etc. Just use the appropriate dice and your own random tables.}

There are no official rules for this.

It's a drawback of the random treasure generation rules: they're incomplete. At the point where you are choosing a particular spell or weapon, you can certainly just pick one, based on what's appropriate to the story or to the party, but if that's how you want to place treasure, why roll randomly at all?

You can use existing 3rd party tools.

I've used Donjon 5e Random Treasure Generator which seems to be a faithful implementation of the treasure tables. It will give you a specific spell or type of weapon/ammunition/armor when it generates something generic like Spell Scroll or +1 item.

You can create your own random tables.

This can be a big time commitment if you want to make tables that could generate any item/spell, even more if you want to do the "daggers more than flails" kind of weighting you mentioned. I started down this path once but quickly realized it was more effort than it was worth for my game. What I ended up using were tables of subsets like "The 1d12 most common weapons" so that I still had something to roll on. And in practice I almost only used it for generating spells because I so rarely rolled +X weapon/armor/ammo.

Be mindful of player expectations.

At one point I generated a spell scroll of the cleric cantrip resistance using my own tables. There was a cleric in the party but he already knew that cantrip (which I didn't realize), so the scroll was basically useless. Both the player of the cleric and another player got kind of annoyed by this. They both expected that if you get a magic item, it should let you do something cool, even if it's a fairly minor item. While I think you should give your players a world that isn't tailored to them, you don't want them to feel shortchanged if they worked hard to get that treasure horde.

First, answering the question as posed: No, there are no rules (actually guidelines) about it, at least I couldn't find any in either the DMG or XGtE, where most of the general guidelines are found.

This is not a problem, though, because when you are DMing, you have two major options: Either you are running a premade campaign or you are running a homebrew campaign. In both cases, you problem can be solved.

Premade Campaign

Most published adventures state the magic item itself, rarely telling you to roll for it. Usually you won't have a problem there. If you do, handle it the same as the homebrew campaign below.

Homebrew Campaign

This is your world. When you wrote this:

Just making the decision myself about what they find, however, feels quite arbitrary.

IMO this is just wrong. You are the world designer. Deciding what monster will be there, how they behave and what treasures the PCs will be rewarded is part of your job, or, if you prefer, is part of your powers. You might think it's arbitrary if you don't put too much thought into it, though, which leads us to...

Give life to the magic items

The DMG has some suggestions on how to create magic items. Check p. 141 for my point.

You can add distinctiveness to a magic item by thinking
about its backstory. Who made the item? Is anything
unusual about its construction? Why was it made, and
how was it originally used? What minor magical quirks
set it apart from other items of its kind? Answering
these questions can help turn a generic magic item,
such as a +llongsword, into a more flavorful discovery.

But don't stop there: Why is the item here? Why is that +1 Longsword, that now we know it's actually the sword of Percival, the Holy Knight of the Kingdom, which was blessed by the High Priest 300 years ago, lost in a freaking Orc Cave? Did they raid Camelot recently and got it as a spoil? The feeling of "arbitrary decision of putting it here" will be nothing to you or your players when you can put a background there, when the item has a plot and simply makes sense for it to be there. That lore can be created before the characters, so you are actually unbiased and not making a world tailored for them.

Obviously be careful with this line so you don't give them too many useless items (for them). But this shouldn't happen in a fairly balanced party - someone will be able to use that staff, dagger and sword.

Additional Official Guidance

You asked about any official guidance that you've missed. I am not aware of additional specific guidance about how to select within the random treasure tables.

However, there is broader guidance that's worth considering.

It's Your World

Chapter 1 of the DMG, It's Your World, talks about "the default assumptions" in the PHB, the MM, and the DMG, and how you might change those assumptions.

Chapter 1 of XGE under, This Is Your Life says:

Even though these pages are full of tables and die rolls, they don’t make up a rules system — in fact, the opposite is true. You can use as much or as little of this material as you desire, and you can make decisions in any order you want.

True, those sections of the DMG and XGE are not specifically talking about treasure tables, but the general guidance might be relevant.

You Can Decide

You asked "what techniques for assigning these sorts of items have you found to work well in your own game?"

Make the Treasure Fit the Story

I find it is often useful to make the treasure fit the story.

The random treasure tables are nice, perhaps particularly for a large horde, but I've found it often makes sense to just decide what the treasure is, and use the treasure tables as idea generators and general guidance.

While it's reasonable to consider what would be interesting to the PCs, I am generally more focused on considering what treasure is reasonable to find at that particular time and place, and let the PCs worry about who gets which what. Heck, eventually (like 2 seconds after they count it up) they'll want to know if they can use their small hill of gold to buy whatever magic item it is that they want. The quest to buy that +1 heavy crossbow can be an adventure all it's own, and may or may not be successful.

Some Examples

Bandits

If the party is confronted by bandits, the bandits would be using any magic items that they have, unless they don't know what the items are or how to use them. So maybe the bandit leader has a +1 sword. When the PCs say, "we search the bodies", (as they seem to say so often), you don't even have to say, "you find a +1 sword", perhaps you give a hint and say, "the bandit leader's sword looks particularly well-crafted". Similarly, other treasure the bandits are carrying might be simple things like a healing potion, although the bandits should actually use it if they get a chance.

Ogres

Ogres, on the other hand, are, according to their description, avaricious and stupid, and live by raiding. As CR 2 monsters, they're unlikely to have accidentally acquired any really powerful magic items, but whatever they've acquired, they might have just left lying around, being too stupid to use or sell it. Since the description says they particularly have a taste for dwarves, halflings, and elves, it is easy to imagine that past victims included a party of dwarves, for instance, and +1 chain and a +1 hammer or battleax might be reasonable things to find in a trash pile in an ogre lair.

An Ancient Temple

As a third example, perhaps they party is investigating an old abandoned temple, lying in ruins for a thousand years, with generations of creatures lairing in it. As the PCs search it, they might find loot reasonable to associate with whatever monsters they defeat, or even previous monsters that have laired there over the centuries, but should they find the chief priest's inner sanctum behind a secret door, they find a room untouched for a millenia, and in it they find items befitting the priest, perhaps vestments that fall apart at a touch, or scrolls of cleric spells, or even a fairly significant item like a Rod of Security or a Scarab of Protection. Or maybe some priestess queen was buried beneath the temple and and items of fearful power were buried with her.

So, what's worked for me is to use the treasure and magic items sections of the books as general guidance, and to make the treasure fit the story.