Like most of the "Do X" achievements in Dead Space, this achievement should unlock easily with time. There are a lot of opportunities to Zero-G jump across the game, but I found myself jumping less often than I would like. For that reason, I just committed 10 minutes in a single chamber to make sure the achievement unlocked.
To perform a Zero-G jump, simply enter a Zero-G chamber, aim like you are aiming your weapon and press Y. If you get a buzzing noise, it means you can't jump to that spot, so pick another. The game doesn't allow you to jump to some surfaces, but you'll pick up on those quickly.
If you want to knock the achievement out quickly, the first Zero-G chamber you will encounter is the therapy chamber in Chapter 2. Simply jump around the room until the achievement pops up. It will take about ten minutes. I found that jumping a very short distance around the chamber was much faster than jumping long distances. This method can be done in any of the Zero-G chambers you encounter, just be sure that you do this in a chamber that has air in it. If a small counter appears on your back and the sound cuts out, you know the room lacks air. You won't have enough time to jump 100 times in a room with no air.