The title says it all, When GMs create NPCs they can do so for a myriad number of reasons. Maybe the PCs need a antagonist or perhaps a PC purchased a Ally maybe the GM just wants to have the NPC fleshed out in case the PCs have need of him. Maybe they are bored and want to create something that may be useful later. Whatever the reason there are a number of ways the GM could go about it. As a GM, I use the following "classes:"
A "fuzzy" NPC is one that has a blip of a entry - if that. It's basically a bunch of cobbled notes that I'm sure many GMs are familiar with.
"Wren the Blacksmith - stubborn and obstinate, but skilled. Armoury skill of at least 12 along with any other skills needed for the making of weapons, armor, etc."
Entry NPC Write-Ups
Entry write-ups are similiar to those in GURPS books for abbreviated NPCs or creatures. They require no point calculation - just GM arbitration.
Wren the Blacksmith
A small, but muscular woman with black hair and black eyes and a tongue sharper than any blade she could possibly forge.
ST 11; DX 10; IQ 10; HT 11.
HP 9 Will 11; Per 10; Speed 5.50; Dodge 8; Parry 7 (Axe/Mace); Move 5.
SM 0; 110 lbs.
Traits: Artificer 2; Appearance (Attractive); Bad Temper (12); Gifted Artist 2; Lifting ST+1; Odious Personal Habit (Curses like a sailor); Single-Minded; Stubbornness; Temperature Tolerance 2 (Heat).
Skills: Armoury/TL3 (Body Armor, Melee Weapons, and Missile Weapons)-14; Artist (Metalworking)-10; Axe/Mace-9; Leatherworking-12; Prospecting-10; Sewing-12; Smith/TL3 (Iron)-13.
Fully Fleshed NPCs
Written up, fully calculated, and otherwise treated as a player character fully-fleshed NPCs (and the work they involve) should really only be done for NPCs you know are going to be reused (like allies, antagonists, or closely associated contacts). When I do write up such characters fully like this for NPCs not bought with points I use a rough scale to determine their point value. First, I add up the entire point value of the PCs and average it. Then I apply the following: 25% of that value for "once-off" NPCs; 50% for "reoccurring" NPCs; 75% for "co-stars"; and 100% to 200% for "stars" or other very important folks.
Wren the Blacksmith
A small, but muscular woman in her early 30s with black hair and black eyes and a tongue sharper than any blade she could possibly forge.
ST 11 ; DX 10 ; IQ 10 ; HT 11 .
Damage 1d-1/1d; BL 24 lbs.; HP 9 ; Will 11 ; Per 10 ; FP 11 .
Basic Speed 5.50 ; Basic Move 5 ; Dodge 8; Parry 7 (Axe/Mace).
5’2”; 110 lbs.
TL: 3 .
CF: Tredroyian .
Languages: Anglish (Native) .
Artificer 2 ; Appearance (Attractive) ; Gifted Artist 2 ; Lifting ST+1 ; Single-Minded ; Temperature Tolerance 2 (Heat) .
Bad Temper (12) [-10]; Odious Personal Habit (Curses like a sailor) [-5]; Reputation -1 (Sharp-Tongued Harriden) [-5]; Stubbornness [-5].
Quirks: Caustic-Tongued; Dislikes people who thinks she "can't do the job;" Likes mining her own ore for forging; Keeps her hair shorn short; Responsive. [‑5]
† Includes +2 from Gifted Artist.