A 5-man army

[Magli]

I almost always have these four pets on me:

wolf (crit buff)
windserpent (magic damage debuff)
raptor (physical damage debuff)
cat (str/agil buff)
x

The last slot varies: if I'm out soloing, I'll have my bear in there; if I'm raiding or have time to prep for an instance, I'll swap in a serpent (sunder) or a hyena (bleed debuff) if I'm in Marks spec or running with a bleed-heavy group. I have a spider for PvP, too, and should probably pick up something that interrupts.

I'd say I run with my wolf more than half the time. For some reason that buff never seems to be covered. My cat, on the other hand, almost never seems to come out, probably because all warrior, DK, and shaman specs provide that buff.

[Heleos]

I'm mainly Marksman during groups, I only use BM for fun pets, and if I have to move around alot during a fight. Therefore I carry:

1) Cat - fav pet and Agi/Str is nice.
2) Corehound - Ancient Hysteria is great when some dps dies and the boss is low, burns em down quick.
3) Turtle - backup tanking
4) Wind Serpent - increases damage of your Arcane Shot.

5) Usually Open for taming.

I never take a wolf because I can't concept when it's better to use Crit buff or Agi buff. Flow chart is hard to memorize. IF anyone has good tips on that - that'd be very helpful.

[Magli]

Heleos,

Install the raid checklist addon here. This puts a button on your window that, when clicked, shows you what buffs and debuffs the other people in your party can bring to the table, highlights missing abilitites, and flags ones you can provide. That makes it easy to scan for missing buffs and see what pet best fills any gaps in coverage.

Of course, you still need to pay attention to whether the other party members actually use their abilities. I was in a run on my Shaman the other day where the DK never once used Horn of Winter, so we weren't getting the str/agil buff. When I noticed we weren't getting the buff, I started dropping the strength of earth totem instead of the armor totem.

[Dolias]

Spirit Beast -agi
Wolf - crit
Core Hound - hero
Beetle - tank
Chimaera - aoe/ranged

thats usually my build

[Araela]

I'm MM with a BM offspec.

In terms of pets, I try to have a variety with me for different needs/buffs.

I generally run with:

1) A cat (Agility/Strength)

2) A wolf (Crit)

3) A corehound (Ancient Hysteria/Blood Lust)

4) A tank (usually my turtle)

5) A spirit beast (heals) OR a dragonhawk (magic damage increase) OR a sithilid/spider/shalespider (for PVP) OR a bird of somesort (for PVP)

It all depends on what I'm doing. I generally don't worry about ravage or bleed effects because 9/10 times they are covered - though I am not saying that those pets are unneeded.

As we speak I have the following active:

1) Cat

2) Wolf

3) Corehound

4) Turtle

5) Owl

I don't know if that helps at all, but that's my two cents on the subject.