grunts- killed with a quick headshot, automatic weapons are less effective, use percision weapons
jackals- when in groups toss a grenade so they expose themselves, when behind the shield hit the exposed hand and finish off with a headshot after it draws back in pain
elites- use plasma based weapons to quickly take down shields, charged plasma pistol works best, finish off with a headshot
hunters- always in pairs so constantly watch your back, use holograms or grenades to distract them then strafe behind one, they only take damage from the rear, avoid getting too close whether you're behind it or not becuase of its deadly melee, constantly jump to avoid fuel rod cannon
must kill prometheans in specific order for best results:
1) watchers- simply shoot it down, best with percision weapon, protects other prometheans from damage so destroy first priority
2) crawlers- do not get stuck in the open around them, easiest to kill with a quick headshot, head is the glowing orange area, automatic weapons work for close range as well
3)knights- save these guys for last, get in their face with an automatic weapon, normally dies from a full clip, sometimes a melee is required to finish it off, always stay moving to avoid its sword and/or scattershot for some knights
ghosts- biggest pain in the neck, destory with rockets or other heavy weapon, soemtimes possible to shoot out the driver, best to EMP with charged plasma pistol then hyjack it
banshees- shoot down with heavy weapon, EMP then hyjack (wont always work in specific missions)
wraith- keep your distances and eliminate the exposed gunner so you can get close, always stay moving to avoid the plasma bombs, oncce gunner is killed EMP then jump on board, plant a grenade or melee until it explodes
hope this helps