If you practice in the Training Arean (TA), there is a green crosshair that follows you and indicates where your bombs will hit if you were to drop them. You can use this along with Innominate's suggestion of alot of practicing to get a better feel.
The green crosshair is also available offline if you configure it under arena settings. (Don't ask me which one of the options it is, I do most of my playing online and I'm not all that familiar with the Arena settings controls).