Don't drop in
The general rule is – one man/woman, one wave. In most cases, you can't have two surfers riding the same wave in the same direction.
When you disrespect the right-of-way rule, you're "burning" someone's wave and showing the utmost lack of respect. You are ruining a wave for someone like you, who also enjoys surfing.
Dropping in may result in severe injuries and damaged surfboards, so don't do to others what you wouldn't want to be done to yourself. Relax, take a deep breath, and wait for your turn. There will always be another wave.
When paddling for a wave, always look both ways to see if someone else is on it. The surfer on the shoulder or further down the line should always give way to a surfer already on the wave. It is possible at some beaches to have a split peak where surfers take off at the same time in different directions (one surfer goes left, one surfer goes right). This requires communication to ensure clarity on the other surfer intentions