As a general rule of thumb, and assuming that you are starting in a good position for receiving serve, if you are ducking out of the way of the ball, then the ball is more than likely going to land in. You should never duck under a ball and let it travel over you head. From that position you have no chance to save it if you realise it’s going to drop on the line.
The best option for a deep serve is to move to the side and watch it as it goes past. Keep your arms high, so that if you do change your mind, they are still close enough that you can play the ball.
in the ideal situation you walk, or run with the ball all the way to the side line, and “track” it as it goes out. Obviously most serves are too fast for that so you just cover it as long as you can, to make sure your decision to let it bounce is a correct one.
This generally goes for indoor volleyball too.