I'll sum it up:
- Go to Un'goro Crater, speak to the trainer to get the quest.
- Take off your clothes and go aggro a handful of Venomhide Ravasaurs. Being naked helps the mobs stay alive for longer.
- The raptors' skin is full of poison - and you have to get splashed by it by hitting them over and over (you can't just stand there). Keep hitting them until they have splashed poison on you 20 times. Note: if you are grouped, you will get credit for other people in your group getting splashed - so group up!
- If you go with a friend and aggro a handful, it will only take 5-10 minutes. If there are lots of people competing for spawns, it may take longer.
- Hand in the quest and get your baby raptor. He will give you a random daily quest each day for 20 days - for example, go kill 20 dinosaurs and feed him the meat. Very simple.
- At the end of the 20 daily quests, return to the trainer with some extra materials (80g 20 Runecloth, 20 Rugged Leather), and you get your mount.
Note: if you are soloing this quest, you'll need to be at least around the level 50 mark, to be able to kill the appropriate mobs. However, this mount can be used from level 40 and up - so if you have some higher level friends who can save you from being eaten by things in Un'goro, you can let them do all the poison-soaking while you get credit too. (I can't find anything that suggests there is a level requirement to accept the quest, so I assume a level 40 can do it)
As an aside - have you bought an Obsidian Hatchling from Breanni in Dalaran? He's adorable. But the little Venomhide hatchling is even TINIER! Of course, he won't be tiny for long; only 20 days if you quest for him every day - then he'll grow up and let you ride around on his back.
Aside from Breanni's, There are also a number of other baby raptors that you can adopt as pets. They are BOU (bind on use), which means you may find them on your local AH.
Keeva keeps a watchful eye over her new charge.
Now, as cool as it is to ride around on raptors and have them as baby pets.. frankly I'm slightly perturbed. Did we learn nothing from Jurassic Park? These animals are SMART. They learned how to open doors. I think we need to ask ourselves - are they just biding their time until they can rise up and eat our faces?
You won't be cooing, "aww, cute" when that happens, will you?
Non-combat pets my foot.
In the meantime, if you're happy to be lulled into a false sense of security, here are some resources to help you:
Wowraid's quick guide to the Ravasaur quest
MMO-Champion shows you which raptors drop the BOU pets
(but when your new pet eats you, don't come crying to me about it.)