NPC Damage types
http://games.chruker.dk/eve_online/damage_types.php
Eve Mission running guide
http://eve-survival.org/wikka.php?wakka=missionreports

Main Damage types to use on NPC's factions:
Corpum - EM & Thermal
Caldari Navy - Thermal/Kinetic
Angles/gisti's - explosive/kenetic
Amarr navy - Thermal
Blood Raiders-Electromagnetic/Thermal
Caldari navy - Kinetic
Blood Raiders-Electromagnetic/Thermal
Caldary Navy-Kinetic
EoM-Kinetic
Guristas-Kinetic
Mercenary-Thermal/EM
Mordu's Legion-Thermal/Kinetic
Roque Drones - EM/Thermal
Sansha-Electromagnetic/Thermal
Serpentis-Thermal/Kinetic
The Syndicate-Kinetic/Thermal
Thukker Tribe-Explosive

Damages types used by NPC's:
Guristas (Caldari) -> Kinetic/Thermal
Angel (Minmatar) -> Explosive
Blood (Amarr) - EM/Thermal
Sansha (Amarr) - EM/Thermal
Serpentis (Gallente) - Kinetic/Thermal