Do
this quest, it will help in dungeons, and even give you something to do while you're medding to scout your next pull. Get your Torch of Alna, Shovel of Ponz, Stein of Ulissa, and Broom of Trilon.
Set up this hotbutton:
/pet back off
/pet attack
Use it whenever a mob comes running for you away from your pet (target said mob, hit the hotbutton, stand in place or run THROUGH the mob, to make sure your pet hits/taunts), also use it to break camps with an earth pet. Send your earth pet into two or three targets, root one, back the pet off, now you can better cleric your pet until root breaks. Pay attention to the "sinks into the ground" messages, take advantage of it, moving your pull if possible so the least amount of mobs are hitting your pet at any given time. Fire pet is another tactic for breaking in, but it'll require more heal spam.
If you know you're going to be dealing with a single hard hitting target, stick to your water pet. If you're dealing with a single target that hits about average for the level, fire pet will be far faster than anything else for the kill.
For travel, keep your earth pet memmed in case you run into some things that can see invis, pop your earth pet out to buy yourself some time to make it to the next zone.
With the level 49 air pet, try it out with two gnoll hide lariats -- most fights, a single mob will stay stunned and do very little damage to your pet.
If you're low on mana, your pet has less than 2 bubbles of health left and can only cast one more pet, one more heal, etc. Most of the time, it's best to just gate, med to full and come back for revenge. A corpse run, is rarely fun.
Always keep your Shielding buff on yourself, refresh it after you haste a pet. In earlier levels, two shield duration fades == time to re-cast Burnout or Burnout II on Gebkn. When you get Arch Shielding, just recast them both at the same time, should be fine. Later on, you can also use levitation (from the rings you summon) to gauge when you need to re-apply your pets damage shield (unless you're using fire, of course), or you can just use the tried and true shaman method -- hit yourself with the buff, then the pet, when it wears on you, it's about to wear on your pet. I rarely find the need to have a damage shield on myself though, every extra point of damage counts only in the most extreme situations.
I think chaining pets in most cases may be more mana efficient, but it's a real pain when you spend all of that mana, and your recent pet summon is light blue and gets eaten before you have a chance to med any of it back. I much prefer the pet cleric method of things, and burn targets down when they're at 30-40%. Seems like too much of a gamble, unless you're trying to kill some red rare spawn. Pets regen HP pretty fast when you tell them to sit out of combat, faster than your mana comes back.