I'm sorry if there is already a post about this topic I thought it would be helpful to the new pet collectors and the experienced collectors as well. There are many addons that are available to you under the Tools button at the top of the page http://www.warcraftpets.com/downloads/pet_addons/ . I use several of them but I'm only going to tell you about three that will help you with collecting. The first on is called Collectinator - This addon provides methods for determining which vanity pets and mounts you're missing to help you in your ongoing collecting efforts. (from WCP.com) when you open up your pets there will be a scan button in the top right corner when you click it another box will open with many options that will tell you what pets/mounts you are missing and how and where to find them.
The second addon is called PetTracker - This addon does several things. It displays the locations of all pets on the world map, tracks all pets you have still to catch in a given zone, displays all your enemies and allies abilities as you fight, and it even suggests which is the most appropriate pet for your current enemy. (from WCR.com) This addon will help you to locate the pets you are looking for. When you open your world map it will show you every pet that is in the current zone and there locations.
The third addon is called Rarity - It was Inspired by Bunny Hunter, Rarity tracks how many chances you've had to obtain various rare items throughout the game. It will tell you how likely you are to obtain the item, track how long you've been farming for it, etc. Provides an LDB feed, tooltips, and progress bar. (from WCP.com) One thing that will help this addon work better is to have the addon Titian Panel it can be found at http://www.Curse.com here is link to it http://www.curse.com/addons/wow/titan-panel.
I'm not the best at writing these things so I hope it all makes sense to you and that your pet collecting becomes much easier and faster for you.
Thanks to WarCraftPets.com and Curse.com for some of the info.