I learned front mount from this video and I just put my phone down to do a bunch of front mounts on a responsive Sage. Keep your non throw hand directly in front of you (centered perfectly) and your non throw hand index finger perfectly parallel to your body. The center of the yoyo should be pointing straight ahead. Doing this with a good solid and straight throw allows you some freedom with your throw hand - like having it over to the right a bit like Adam does in the video. It just takes practice. I find with frontstyle tricks you really need to keep both your index fingers very straight / parallel to your body. From the Yonomicon:
It just takes loads of practice. You WILL get it.
I start most frontstyle with this front mount. When I throw the initial sleeper I always throw down a bit off center to my right. For some reason this keeps everything lined up perfectly when I get into the front mount.