Things to consider when box kicking:
Make sure body shape is nice a square to the bi-line and your first step is about 45 degrees back.
Keep you arm out pointing the opposition's sideline to make sure you don't over rotate on the ball.
Get a ball tilt of about 45 degrees back to your try line
The contact point should be in the bottom third of the ball
Keep your head down for consistency
Get a forward in position to protect your kick from the charge down, making sure he does not move and get called for obstruction.