For NPCs I use the following
-first I determine how important the NPC is. For important and nasty villains for example I scavenge sometimes the Gurps book "villains" for ideas. For warriors I use the Gurps warriors book too
Then I do detailed stats as for PCs.
-For not so important NPCs I use just generic templates. Eg. an average clan-warrior has 50% weapon skills, sometimes d4 damage bonus, DEX11 and 11 HP, armor fur or leather, eg. an elite warrior from the cult of the red snake has 65%, always +d4 damage bonus, DEX13 and 13 HP. armor up to mail,
Sometimes I vary the stats +-3 points to generate more different types the players encounter.
Also for variation I give them certain easy to remember key words for
-clothing (blue hat with feathers, nice ornamented boots...)
-appearance (wart on his nose, different eye colours, dark skinned, bad teeth....)
-behaviour (giggling, studdering, waving alot with hands - like italians, never look in the eyes of others, arrogant, VERY friendly, helpful, aggressive...)