NPG Story Role:The first step is to identify the role that the given NPG will play in the development of the story, in much the same manner as for individual NPCs. Some of these story-roles can be combined, although "Scenery," as a role, is assumed to be part of any other.
NPG Character:The next step is to treat the NPG as if it were an individual character. Decide how you intend the group to interact with, and come across to the PCs. Ideally, you should find a character or person you are familiar with to serve as the "inspiration" for the NPG. Describe this character as if the Players is meeting it for the first time, then adapt that description to fit the group as a whole. Essentially, this step develops the character of the "average" member of the group—the Extra—and determines the baseline from which the individual stand-out characters will deviate. Conditions for consideration, here, might include such concepts as morality, wealth/poverty, piety, order/chaos, belief(s), etc. Consider all the usual individual character traits (IE Stats) for the group. For NPGs whose story-role is no more than "Scenery," and no direct social interaction is allowed for, this may be all the detail that is needed.
NPG Drama Level:Drama Level represents the amount of variation from the specified baseline description, the likelihood of tensions between opposing Roles turning into actions, how well the group works together towards it's common goals, and it's tendency to fly apart when tested. High Drama means that fighting-to-the-death could easily result from a disagreement, and the Roles are distinct and easily recognized. In a low Drama situation, the same disagreement might result in little more than a quip and/or hard feelings, and the Roles might be difficult to tell apart at a glance, as there is little variation between the characters (e.g. the Hero and the Villain aren't really all that different, morally—maybe the Villain is more of a prankster or rival than an actual "enemy").
NPG Complexity:The two primary axes are Constructive/Destructive (C/D) and Proactive/Reactive (P/R). The C/D axis refers to the tendency to promote order or chaos within, and to further or hinder the best interests of the group; generating versus eliminating problems. The P/R axis refers to the tendency toward aggressive or passive action, recklessness or caution. At the center is Neutral, which applies to any Element that doesn't truly serve any of those purposes, or is inconsistent.
NPG Complexity defines which axes of the alignment compass are used to determine the effect of the active Elements. For simple NPGs, definition of a single axis might be enough detail. More complexity warrants two axes, either straight up (C/D,P/R) or the secondary axes, or "corners" (CP/DR,PD/CR). Higher complexity groups will exhibit the full range of the compass (or possibly more, if using a 16-point compass; e.g. "Leanings," in D&D's moral alignment). All Elements will be assigned to these Alignment points.
The primary Elements in any NPG will "drive" the group based on the alignment of their Element; this represents the "pull" that the presence of that Element exhibits. This works exactly as for D&D's "moral" alignment, but instead of being based on virtues like Good & Evil, it is based on the Element's overall effect on the NPG, socially and/or functionally. This NPG Alignment is entirely separate from the personality or intent of the Element in question; a character may intend to serve the best interests of the group, while tearing it apart. NPG Alignment is also not related to it's "morality"; an NPG could have an "Evil" character in a "positive" Role.
A given NPG need not be balanced, when it comes to its Alignment. In fact, an NPG, as a whole, will tend to be more motivated in the "strong" direction, and so a little intentional imbalance might be desirable, depending on the character of the group.
NPG Depth:The PCs, generally, will only socially interact (in detail) with a relatively small percentage of the overall group—in cinema, the ones whose actors' names are in the credits. Only the important characters should be assigned Roles; the rest are Extras (and will follow the indicated baseline). NPG Depth, in essence, is the number of independent characters or character groups that will be detailed and assigned to Elements. With larger numbers of these Elements, they should be divided into the following Tiers. Tier1 Elements include the most visible characters, with whom there is to be regular interaction; these can be expected to always be a factor in NPG-related events. These are the Elements that will "drive the car." These will generally be a small number of the most vivid characters. In simpler NPGs, these will likely be the only characters with any detail. Tier2 Elements include those characters that have a similar but lesser degree of detail as the Teir1 characters, are not always "central" to NPG-related events, and whose Roles may not be as clearly-defined. These Elements don't "drive the car," but they do "help navigate." The sidekicks. These will generally make up the majority of the NPG's Elements. Tier3 Elements are "glorified Extras," having names and maybe a little detail, and are encountered on a recurring basis, but have no "driving" Role other than Scenery. These Elements are merely "passengers," and have little effect on the direction of the group—no Role or Alignment is necessary (but can be assigned). Peripheral Elements are recurring characters, maybe detailed or not, that have an effect on the NPG, but aren't exactly a part of it. They may have an assigned Role, but will exert that influence only on rare occasions. These Elements are "other drivers" on the same stratch of road.
NPG Element Roles:Element Roles are, essentially, commonly encountered character stereotypes. Each point of the chosen alignment compass is a Tier1 Element, and is assigned a Role. The Element may be an individual character, or that individual might have a backup/buddy/counterpart/partner/family, or an entire "posse," or be an entire, fully-detailed, sub-NPG unto itself; these can be mixed-&-matched as well, having an Element representing an individual and one representing a full posse in the same NPG. For greater depth-levels, Tier2 will generally have multiple Elements per Alignment point, and will also be assigned a Role (though that Role will be weaker than Tier1). Each Element needs at least one Role assigned to it. Any given Element Role may be filled by multiple Elements (esp. for large-scale NPGs), and any given Element may fill multiple Roles (esp. for small-scale NPGs). The assigned Role(s) will then dictate the "handling" of that individual(s), and suggest appropriate characteristics when fleshing out the characters' details. Here are some examples of common Roles (I have included my short-hand notation in parentheses):
If a character's only purpose to the group is as the "significant other" or "Partner" of another character, then they should be considered a sub-Element of that Element—only if they serve a purpose to the group as a whole should they be considered separately. For handling purposes, those characters should be treated as for the Tier below their controlling Element.
NPG Element Interactions:
Golden Rule of Drama: if potential for conflict is visible, it will never be passed over. Most Roles have a direct opposite, their focus of conflict, the point where drama will ensue.
With each other:The Villain will be suspected of whatever goes wrong, and the Group will look to the Hero to fix it. The Challenger will always try to subvert/question the Boss' command, either to take it for himself, or for another. The Snoop will always keep an eye on, and the Gossip will offer opinions about, the Mystery. Everyone looks up to the Superstar, and shuns the Outsider (who probably wants to be the Superstar). Characters who share the same Element Role will either find themselves in agreement on the issue-of-the-day, and will work together, or will "compete," and be opposed to each other.
With PCs:Upper will invite PCs into the festivities, and the Downer will ignore/snub them. Idiot will stumble across PCs' secrets. Hero will encourage the group to aid the PCs, Villian will be suspicious of them. Villian will treat PCs as its Victim. Superstar & Outsider will usually be easy to spot.
NPG Fluidity:When things get stressful for the NPG, Drama Level will be effectively increased by a step or two for the duration. Over time, things change, and Roles will change. As individuals leave the group, or come in, Roles may be swapped. There will always be a Boss—someone will step up or be chosen by the rest, intentionally or otherwise. These normal changes may result in imbalance, but over time, the imbalance should correct itself, as individuals transfer in or out—also, intentional or otherwise.
Example: Lost, Season 1:Survivors of Flight 815 (Surv):
S:Focus; D4; Char: A bit imbalanced in the Destructive direction (always threatening to break apart)
Tier1 Elements:Jack (Surv) R/Bss,Skp,Hro1
Locke (Surv) C/Wiz,Chr,Upr
Sawyer (Surv) D/Jrk,Scd,Vln1
Kate (Surv) P/WC,Hro2
Tier2 Elements:Michael+Walt (Surv) P/Idt
Hurley (Surv) R/Upr,Hlr
Boone (Surv) C/Tag1
Charlie (Surv) C/Tag2
Sayid (Surv) C/Scd, Fxr
Claire (Surv) D/WC
Sun+Jin (Surv) D/Mst,Vln2
Shannon (Surv) D/Jrk,Idt
Tier3 Elements:Rose (Surv) N/Xtr
Arzt (Surv) N/Xtr
Example: Jericho, Season 1:Jericho Residents (Jericho): S:Focus; Char:
Tier1 Elements:Jake (Jericho) P/Hro1,Scd1
Hawkins+ (Jericho) C/Fxr,Mst,Wiz1,Scd2
Johnston+Gail (Jericho) R/Bss,Wiz2
Gray (Jericho) D/Chr,Vln,WC,Dnr
Tier2 Elements:Stanley+ (Jericho) P/Hro3,Upr,Tag1
Eric+ (Jericho) R/Dsl,Tag2
Emily (Jericho) N/Scd3,Tag3
Heather (Jericho) C/Vic,Upr
Jimmy (Jericho) C/Idt,Upr
Bill (Jericho) D/Idt,Dnr
Dale+Skylar (Jericho) D/Vic
Tier3 Elements:Gracie (Jericho) D/Xtr
Peripheral Elements:Jonah (Jericho) D/Vln