Now I consider thread jacking to be a virtual art form. However, just for a little variety I decided to pull this quote out of the Artificer thread and answer it in its own thread.
Without diving headfirst into the lengthy back and forth going on here, I did want to point out two situations that merit having a system for "regular" people (be that a 1st level commoner or a 5th level expert, 3rd level aristocrat, etc.)
1) The PCs are talking with the NPC, get upset with them and attack. I want to be able to run that combat for a round or two to see if they kill the NPC before the guards and/or the NPCs buddies come to see what's going on. Using the minion rules of one hit = one kill is too simplistic in my opinion - if you can roll a 1 on damage, that shouldn't necessarily kill the guy - while he might not be a challenge or important, whether he lives or dies can be important in terms of the consequences - assault vs. murder charges in this case.
2) The PCs rescue one or more NPC prisoners, but have to keep them alive on the way out of the dungeon (or are escorting a mechant and his family through dangerous terrain, etc.) Knowing their combat stats might be important if some of the real opponents can slip past the PCs and start fighting the soft yummie easy targets. An example of this type of scenario can be found in Paizo's very own Rise of the Runelords very first scene, when protecting the town from a goblin attack.
OK I can see this point. Now I think others, such as David Marks, have pointed out a number of good ways of creating human commoners as monsters and such and I think those ways would really work. Still if your set on having a Commoner Class it dawns on me that it might be pretty easy to create a pretty authentic feeling one. Works like this:
If you look at the classes in the PHB you'll notice that every class starts with this table called CLASS TRAITS. Everything after this table is all sorts of cool class features and powers for the individual classes presented. Thing is we can fill out that first table for the Commoner and not worry about cool powers or wicked class features - he or she is a commoner and does not get any cool class features or neat powers. OK so here goes:
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CLASS TRAITS
Role: Plot Exposition. Pray; on your knees; in the dirt; that your purpose in life is not to die a grisly death at the hands of one of the DMs monsters. If your really lucky you'll be the cute female that the PCs will save - or the child, that pretty much grants you immunity if the DM uses a screen.
Power Source: None. Shya right, you wish
Key Abilities: None really or as dictated by plot or th NPCs job.
Armour Proficiencies: Cloth, sometimes also Hide. If your some cool NPC like a Fantasy Mohawk Indian then you can wear animal furs.
Weapon Proficiencies: Simple Melee, Simple Ranged or, occasionally, as dictated by job or plot.
Implements: None.
Bonus to Defence: None. Well their is DM fiat. Repeat after me...Please be good DM fiat...Please be good DM fiat, I don't want to be the guy that expires from his wounds seconds after giving the PCs their new quest.
Hit Points at First Level: 10+Constitution Score. This is the same as the wizard who is probably the most 'Commoner like' class in many ways as he or she is a Commoner that wields magic. This is probably good for clerks, fat bar keeps and the like. Making it 12 through 16 + constitution score is reasonable if the Commoner is a Farmer or hard working Miner or a Commoner with a job or role that makes him or her particularly tough.
Hit Points Gained Per Level: None or 4 through 6. I'd say none but 4 would be the same as the Wizard. My feeling here is that Commoners just don't have levels, Thats for PCs or NPCs with other classes. If they kill Goblins or some such they morph into a PC class like Fighter or Ranger or some such. Essentially if they do something special then they become something special just like the PCs. But if your really disagree with me on this I suppose 4 through 6 would be valid depending on what the NPCs role or job is.
Healing Surges Per day: 1 + Constitution Modifier. 6 would be the wizard. Here though this might just be a too much for an NPC. Two or three (depending on that con score) is probably a better choice. Enough that the PCs can be trying to dramatically save the NPC without things just devolving into some kind of lunacy with the Terrible Monster dropping the Commoner and the PCs using healing or some such to bring him back round after round like some kind of Monty Python skit - I'm dead...no I'm not...wait yes I am...Thank God I'm back...Aw shucks, I'm dead again...I've returned!...Crud, killed again...
Trained Skills:Whatever is demanded by the plot, role or job.
Build Options: Gruff Dwarven Armourer, Busty Tavern Wench, Effusive Shop Owner, Worshipful Street Urchin, Aloof Elven Artisan...The list just goes on and on.
Class Features: Free skills and feats based on DM fiat.
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Ability Scores
Now this gives you the basics of a class. If you wanted to fill out a character sheet you'd need two more aspects of your NPC. You'd need to know his or her Ability Scores. You can set them based on some presumption of what Commoners represent, for example 8,9,10,11,12,13. I figure every DM has to decide what kind of ability scores the Commoners get in their campaign world. I'd probably be a little more generous then the above and then assume that Commoners that morph into character classes get a boost to their Ability Points to make them equal to the PCs and that this represents training or a flowering of talent that came out when the Commoner morphed into a PC class.
Race
The other thing you need to know about your Commoner is race. I'd just apply the race as per normal. Presumably all Dragonborn can breathe (they must have really nasty domestic disputes).
Finis
Now you should have everything you need to fill out a character sheet. If you have weapons you always attack using the base attack.
Good idea on the post...especially trying to remove this discussion from the Artificer post.
I would suggest that you could use the steps in the DMG for designing NPCs to create a commoner.
1. Choose Level: I would put forth that a commoner would effectively be level 0.
2. Choose Race and Class: Race as per normal, class = Commoner
3. Determine Ability Scores: THis is one of the steps I would alter somewhat. My suggetion would be to start of with the basic array that you start off with as PC's before doing point buy: 10,10,10,10,10,8. You would then apply the ability bonuses based on race.
4. Hit Points and Healing Surges: Healing surges would be 1 as per the guidelines. As for Hit Points, I would agree with the OP and go with those of a wizard.
5. Calculate Defenses: 10 + 1/2 level + ability modifer and then add in any bonuses due to race. As the commoner is effectively level 0, there is no Level Bonus to add in.
6. Choose Powers: Skip this step.
7. Choose Skills: Choose one or two skills to be trained in. THis should be determined by the role you want the commoner to fill. If he/she is to be a farmer, choose Nature and Athletics. A beggar? Choose Streetwise and Thievery. An Aristocrat? Choose Diplomacy and History. (All just suggestions)
8. Choose Equipment:Would be determined by commoner role
9. Calculate Attack and Damage bonuses: As you do for a PC
10. Choose Rituals: Give scrolls if appropriate to role.
Not too shabby, and thanks for the props! One of the new features over at the new version of ENWorld's boards is the ability to "fork" a thread, and spin off a threadjack into its own new thread. Very nifty, and helps prevent threadjacks.
I like your concept, although the healing surges are a bit high (I'd stick with standard DMG rules and just give 1 per tier)
I'd be careful re: the situation with rituals ... you don't want to have to create 8th level Healers just so they can perform a Raise Dead ritual, frex. Still, for those trying to capture this type of feel, this will serve pretty well. Thanks!
3. Determine Ability Scores: THis is one of the steps I would alter somewhat. My suggetion would be to start of with the basic array that you start off with as PC's before doing point buy: 10,10,10,10,10,8. You would then apply the ability bonuses based on race.
Well my main reason for choosing some form of array or even just assigning stats by DM fiat would be to distinguish commoners from each other. If their not going to be used as a pretty full fledged NPC then the idea of statting them up make no sense at all. Even in 3.5 nobody statted up NPCs that were not really significant. A good array helps here mainly as a place to start and as a thinking exercise. Whats this NPC unusually good at versus what the NPC is unusually bad at.
Thus I think if we have reached a place where an NPC is so important that we feel the need to stat them up then we have also reached a place where they need to differ from each other in abilities with some being smarter then others or stronger etc. This is especially true since the majority of NPCs that are statted up are humans and have no bonus' to stats.