I play R/Mo a lot and this is my bread-and-butter PUG/henchie build for when I'm feeling lazy. It's not the best build out there by a long way, but it does allow you to do decent offence and interrupts while providing emergency defence. It's a PVE build.
Marksmanship 11+1+1
Expertise 12+1
Beast Mastery 3+1
Wilderness Survival 5+1
Protection Prayers 2 (because I have a handful of points left over)
I've never even got round to picking up a Superior Marksmanship Rune, but would recommend it. That'll up your attribute from 13 to 15.
Tiger's Fury
Barrage {E}
Marauder's Shot
Concussion Shot
Distracting Shot
Throw Dirt
Troll Unguent
Rebirth
I use 3 bows, an elemental string bow for when I'm not fighting or if I'm up against a warrior mob, a vamp bow for general damage dealing, and a zealous bow to recover energy during a fight (imporant if you're using concussion shot).
Tactics are pretty basic. Stay by the back rank casters, preferably the healer. Spam Tiger's Fury, which at BM rank 4 gives you an increased attack speed for 7 out of every 10 seconds. Use Marauder's shot to help spike any called targets, and barrage to keep up a decent damage rate. Because Expertise 13 makes your 5 point skills cost only 2, you can keep this up for a long time, especially if you switch to the zealous bow.
If you're up against a caster threat, stop spamming barrrage, and fire off a concussion shot, you can also use distract if you're up against a spammed enemy skill.
If (as happens a lot in Factions) the enemy warriors/assassins try to mob your casters or you, use Throw Dirt to buy you and the casters a bit of time, and either retreat and use troll's or call a spike on the enemies while they are still blinded.
If the brown stuff really hits the fan, you can use Rebirth to pull people out of the action and dust yourselves off.
If you know you're going to be teaming up with other rangers, then sub out one of the interrrupts for a spirit. Other variations are to replace barrage with a preparation, which also allows you to pick a different Elite - Poison Arrow or Escape for example. If you do use a preparation, you may also want to consider replacing one of your interrupts with Needling Shot, as the extra damage from the preparation stacks up nicely.
However you do it, the main philosophy is to have at least one cheap skill that does regular damage (which is why I like to use Barrage, even if it's a bit lame

), a good 'spiking' skill to help take down priority targets (Marauder's does that job here) an interrupt, a good emergency defence and a reusable res spell.
If yo want to heal people too, then go for a different build like the one above, but IMHO rangers do not make good healers becasue of energy management issues. If you need to be healing people in the first place, then you've probably got a bigger problem... which is where the reusable res comes in
really handy!
Hope this helps,
Doug