Just as Villages are often glossed over, so are the inns that adventurers often stay in during their travels. Still, there are times when a little detail can be useful, both for the inn itself and for whatever other NPC's are staying the night there as well.
First, the name of the Inn in question. Roll d4 twice to get started (if you roll a 4 on the first roll, use a d3 for the second roll instead) to see what type of words forms the name of the Inn.
If there is an Adjective, it always comes first. A Person will come first, unless there is also an Adjective. A Creature will always come last. If there is no Adjective, then there will be an '&' between the two names. Add 'Inn' at the end of it, and there you go.
PERSON (roll d20)
OBJECT (roll d30)
CREATURE (roll d6,d6)
ADJECTIVE (roll d30)
26. Ye Olde
30. (roll twice on this table)
For Number, roll d8+1, giving a range of adjectives from Two to Nine (anything following should be plural, or course). For either Color or Metal/Jewel, roll on the subtables below:
COLOR SUBTABLE (roll d8)
METAL/JEWEL SUBTABLE (roll d8)
As for the inn itself, if it is situated in a village, it will have 2d4+2 rooms that it rents out, in addition to the common room. If it has 8+ rooms, there is a 1-in-6 chance the building has two stories, otherwise it is an one-story structure. If in a town or city, the inn will have 3d6+2 rooms for rent (plus common room); assume any such structure with 11+ rooms is automatically a two-story building Most rooms can hold two human-sized travelers for the night with minimum fuss. There is a 2-in-6 chance of there being a stable nearby for the horses (or really poor travelers). There will be 1-2 primary owners (if two, even odds of it being a married couple), with a number of servers and other help equal to 1d3 + (number of rooms for rent/5, +1 if there is also a stable), most of them probably related to the owner(s). There is a 1-in-20 chance of the Innkeeper(s) being Eeeeeeevil (i.e. spy for foreign power, dangerous cultist, or just killing travelers via secret doors into the rooms so they can steal their gold and make meat pies from their bodies).
Of course, there's no guarantee that there are going to be enough rooms for all of the PC's to sleep in. That depends, after all, on what other travelers are staying overnight there. Roll three times on the Common Travelers table below if in a village, four times if in a town or city; roll an extra time if there is a fair or religious festival going on in the area at the time.
COMMON TRAVELERS (roll d8)
1. 2d3 common craftsmen (i.e. potters, masons, etc) traveling between towns, probably staying in the common room.
2. 2d4 criminals - could be local members of the thieves' guild, bandits, slavers, etc. Might be staying in the common room, or might be renting rooms (two per room). Probably won't attack while in the inn, but may ambush the PC's if they don't look strong enough. Most will be 1st level, but the leader will be 1d4+1 level.
3. 2d4 fighters, possibly either traveling guardsmen, or mercenaries for hire. Even odds whether they are renting rooms or sleeping in the common room. 1st level, with a leader 1d4+1 level.
4. 1d3 locals, probably sleeping in the common room because they don't want to go home this particular night. If more than one, they might be getting together for some secret meeting (conspirators, sexual tryst, etc.), in which case they will have rented a room.
5. 1d2 merchants, renting rooms (possibly a room each). Will have 2d3 1st level fighters as guards with them, who may or may not be sleeping in the common room, and 1d3-1 apprentices, who will definately be sleeping in the common room.
6. 1 lesser member of nobility, who will (of course) have a room to themselves. They will have 1d3 guards (1d4 level fighters) and 1d2 servants with them, who will also be sleeping two to a room.
7. 2d4 pilgrims, all sleeping in the common room. There is a 1-in-10 chance that one of the pilgrims is actually an adventurer or former adventurer (roll as per Uncommon Traveler, below). There is a 1-in-6 chance there is a Cleric with them (1d6 level), probably renting a room for themselves.
8. roll on the Uncommon Travelers table below
UNCOMMON TRAVELERS (roll d12)
(assume that there is only one of each, unless otherwise mentioned, 2d4 level, and will definitely have a room to themselves, 3-in-10 chance is actually a demi-human)
4. Cleric (even odds 1d6 acolytes are with them, either two to a room or sleeping in the common room, 1-in-20 chance is a Druid instead)
6. Knight (4-in-6 chance has a 1st level squire with them, in their own room)
7. Magician (1-in-10 chance is an Illusionist instead)
11. Adventurers (2d3+1 in number, 2d3 level each, reroll d10 on this table to determine class for each)
12. roll on the Special Travelers table below
SPECIAL TRAVELERS (roll d6)
(all except the last option will, of course, be shapeshifted to appear human (or at least humanoid), all will be alone unless noted, and all will have rooms to themselves except where noted)
1. Demon (probably a Succubus)
3. Dragon (either Silver or Gold)
5. Lycanthropes (either 1d3 werewolves or 1d4 wererats, either sharing rooms or sleeping in the common room)
6. Ghost (not actually renting a room, of course... the inn is haunted!)