On my final dives with my students we play a game: who would you dive with and who should you avoid? I want them to ID divers on the boat they would want to emulate and those who they should avoid. It's not to make them feel superior, but to make them start to make conscious choices about who they will dive with as well as how to attract good divers. After all, the best accident is the one you prevent from happening or at least avoid. The only way to learn how to choose your dive partner wisely, is start being critical of the divers around you. Not to be mean, but in order to preserve yourself and your fun. They look for danglies, nervousness, fear, over confidence, FIGJAMs, new equip, abused equipment and so on. It adds a bit of self applied peer pressure as they realize that divers are doing the same thing to them.
So critique other divers. Learn their good habits and avoid their bad ones. Be careful about voicing your opinion to them. Many don't care what you think and will actually resent you pointing out their deficiencies. Keep your observations to yourself for the most part. You'll know when you can share them.