How about some general tips?
If you're trying to capture, grab a Terrible Turnip asap, and level it up. It has the ability to leave the enemy pet with 1hp, so you can use the TT to trap any level pet.
I just picked this up, but I'd recommend getting this add-on --> www.petsear.ch/addons it's available on Curse.
It gives you the pet breed information of your pets and the pets you're battling, as well as the potential breeds of each pet type.
If you're not familiar with breed, there are 10 different breeds (http://www.warcraftpets.com/wow-pet-battles/#breeds) possible, although most pets only come in a couple different breeds. In general, though, there are Health (H), Power (P), Speed (S). Or, pets that are Balanced (B) stats. Breeds can be have all points in one of the stats, stats in 2 of the 3 stats, or all three stats. These points affect the formula for base stats and level-up gains. The pure pets like P/P for power pet, or S/S for speed will be really good at that one attribute, i.e., more powerful, faster, or more health. The pets with points in all three will not be as strong.
The add-on I linked above displays the P/P, S/S, etc. on the pet info. I've only begun to check this out, but I think it will end up being really important as I try to progress in battling.
Edited, Jan 10th 2013 10:42am by azwing