Pro Pet Group

You may be asking yourself: "What's to stop me from capturing level 24 creatures to minimize my effort on this one?"

The answer: Nothing's stopping you. It works.

At this moment, if a pet which has reached level 25 is reduced to level 24 or 23 due to the use of a battle-stone, leveling it to 25 again will count toward the achievement.

The Incursion in Krasarang Wilds is a great place to level pets. Lots of wild battle pets in the area, a stable master right there for heals, and a good variety of secondary pets in case you're farming rares at the same time. Take a few runs to the nearby beach for even more pet variety.

And if you want to use the XP you can get while working on this achievement to level an alt, there's a flight path and an inn right there (tent behind the drunken-looking mage). You'll need to be high enough to reach it the first time, of course, but there's a lot of XP between 85 and 90. Might as well knock some of it out at the same time.