I only did collection quests if the drop rate was high with a fast respawn rate, otherwise I skipped it.

I would check with Wowhead.com to see if there are any complaints of the drop rate.

If you are talking about pick up, as it, quests that you require you to pick stuff off the ground, like the parts quest in Hellfire... I just do them as I do the other quests.

I usually start with the toon with lowest XP, so if I get sick of it, that toon can turn it in and try to catch up to the others.