WoWDB

To earn this achievement, speak with Maxima Blastenheimer next to the massive cannon on Darkmoon Faire island.  You do NOT need to be on the daily quest The Humanoid Cannonball to earn this achievement.  For the cost of one token, you will get loaded inside the cannon and fired across the faire towards a floating ring on the south-east corner of the island just off the beach.  You will be given a special action bar to allow you to drop from the air into the ring, and your goal is to land in the exact middle.

• A central hit grants five points and earns the achievement.
• A near hit is worth three points.
• If you're at the edge of the ring, but are still inside, you get one point.
• If you miss entirely, NOTHIN' SUCKA.

One of the best strategies for landing a bullseye is to angle your camera directly downward while flying, and hit your drop button as soon as you are over the boardwalk.  Due to latency and other factors, this may not always produce the right timing, but it is a generally good strategy.

Also, if you don't feel like hoofing it all the way back to Maxima Blastenheimer after each try, there is an NPC gnome fishing on the beach near the ring named Teleportologist Fozlebub who will teleport you Back to the Cannon! for a small fee.