I would reccomend one of the following three skills.
For maximun damage output go with Shooting Wild, it removes your aimer and laser sighting but that doesnt matter for certain guns like the shotgun and assault riffle were if your close enough you can't really miss. I find that using the crossbow with Shooting Wild is insanely overpowered, only thing is it takes alot of practice to learn to shoot without an aimer but pays off when you can pull it off, a major plus is you can still use quickshot to fire off an auto aimed shot.
If you want to do good damage but want keep your aimer then just go with Target Master, but I think thats only available on onslaught and not Predator, plus the amount of damage done is not as high as with the Shooting Wild skill and also this causes your melee damage to do almost zero damage, when using Target Master only use melee as a stun and not for damage.
If you want to survive longer and don't care about added damage increase then use pharmacist for added health recovery when you use tablets, this is the skill I'd recomend mostly because more health is always good and there is not strings attactched like the other two skills.
A faq is not needed...as the previous user said, it depends on the individual's play style. Shooting Wild and Pharmacist are probably the best 2 for Predator. Quickshot Damage increase for people who like using Helena's quickshot with her shotgun to get roughly 1,000 points each shot. Carla + Shooting Wild is probably the best setup though. Cheap IMO if there is 2 or more people using her in a game. I haven't played Onslaught since the zombie kill event last month, but I think I just used Power Counter since there was plenty of health around the maps.
As a Carla main who uses Shooting Wild, I can confirm that it's one of the best setups there is. She has long and short range with huge point potential. If Ustanak grabs somebody near you (or at all) you can unload both guns entirely, doing massive damage and gaining crazy points. If you pick up any gun drops, break his shotgun, or heal any Agents, it's hard to deny her point potential.
But Shooting Wild works with practically anyone. If you have decent aim Shooting Wild + machine guns is quite a lot of points. The only other skill set up that I see people using is Jake + Martial Arts Master. Personally I don't think it's worth it to have to stay so close to Ustanak the whole time, but the point/stun potential is pretty high.
I think Shooting Wild is hands down the skill to use in Predator. It makes any character a damage and point-gathering powerhouse.