This is the type of tricks I need! So, how does the stats for a typical city guard look like? And how would it differ from a "veteran city guard"?
Personally I don't normally bother with Characteristics (STR, CON etc) for a throwaway generic NPC. I will give them Attributes however, if it looks like they might need to fight.
So for example. On Monday night, a new player decided to ambush a street beggar in the hopes of capturing him alive for some more nefarious purposes. Sadly, he decided to overlook the fact that the beggar had seen right through his feeble attempts to coerce him out of his blind alleyway and was suspicious. Instead the PC attempted a brute force approach, confident in his ability to beat up a near defenceless, one-armed man.
Caught somewhat unprepared for the mugging of an innocent beggar, I created one off the top of my head. Now in the campaign (Monster Island) almost everyone in the colony are hardened mercenaries, treasure hunters and merchants seeking to plunder the island's resources. Most die, but those that end up beggars are generally tough types, who have lost limbs to savage monsters or their minds to dangerous narcotics. I decided therefore that this particular beggar was:
One Armed Beggar 65% (ex-warrior: 85% Hard Bitten Beggar combat style), 3 AP, +1d2 DM, +14 SR, 5/7/6/4/5 HP, no armour.
2 seconds thought, bang, done. Notice that I gave him an increased secondary skill, to represent his previous profession. So during the initial negotiation the beggar used the Insight and Conceal skills at 65%, but once fighting broke out, he utilised his higher combat skill.
Unfortunately for the player character, despite being armed with a sword, the beggar managed to fend off the first attacks with his begging stick, before it was knocked from his hand. So, once disarmed, the beggar stepped in close, tripped the PC with a grapple, and then proceeded to throttle him into unconsciousness...
As for competence levels I use the following guidelines, which are printed in Monster Island. Sorry about the formatting, its a rough translation from a table.
Skill Value - Professional Competence - Military Equivalent - Description
1-30% - Novice - Cannon Fodder - Unqualified student still learning the basics
31-50% - Competent - Green - Can perform easy tasks if taking their time over it
51-70% - Proficient - Seasoned - Has reached an employable level of competence
71-90% - Expert - Veteran - Has spent years as a professional
91-110% - Master - Elite - Is considered one of the best the local community offers
> 110% - Paragon - Heroic - Renowned far and wide for their consummate skill