This is EXACTLY where I was at not to long ago. I created my own acronym to help me: DISC GARF.
GARF= Grip, Arm, Release, Follow Through.
Grip= making sure I have good traction, with my fingers up in the rim, and most importantly my thumb FLAT pressing down firmly. I found this helps me keep the nose down, and prevents unwanted hyzers.
ARM: my arm is coming straight through my body, not swinging out, and that it accelerates in a line parallel to the ground,
Release: not locking my wrist, keeping it lose, but not flexed inward. Getting a good flick, or snap at the end of the throw, which naturally happens with a relaxed wrist, and firm grip, making sure I'm releasing the disc, and especially the nose flat.
Follow through: swinging through the throw, turning my whole body in one timely motion. This is a very important part. You want to make sure your not turning your hips too early, (hyzer) or too late (flies too high) combining all these elements and working the Beto drill got me to 400'