1.) Should you be fishing in a location where you can drive your vehicle up to the stream bank, & should you decide to do so (for ease of access & less walking) parking your vehicle less than twenty feet behind you, make sure to mind your back cast. Snagging your windshield wiper is not good for your wiper, hook, or your pride.
2.) If you should accidentally drop something buoyant into the stream, like a fly box or other type of container & need to move downstream to retrieve it, please do so calmly. Running as fast as you can down a very narrow stream-side path in the exact direction of another unsuspecting angler while yelling "I'm gonna get it!! I'm gonna get it!!" may not be a good idea. This is especially true if the other angler on the path, who by now has a very worried look on their face as you approach, is a lot bigger than you.
3.)Do you carry your cell phone in your fishing vest? That might be a good idea - for safety, should you have an emergency. However, you might not like the reaction from other anglers if you carry on a loud conversation over your phone while standing under a bridge, holding the phone in one hand & casting your rod with the other. Hint: voices carry & being under a bridge amplifies your voice. Although it's good to know what you'll be having for dinner later tonight & that your wife already fed the dog.
4.) I'm all for being friendly & pleasant with the other anglers I encounter along the stream. That being said, if you're up on a high, steep bank & spot another angler fishing the deep water directly below you, you might want to refrain from walking right up to the edge of the bank so the fish can see you, then spitting into the water (actually hitting the angler's line with your discharge) & asking them "doin' any good?". Do that & you're almost certain to have a short conversation that doesn't end well.
I know proper stream etiquette can be a confusing, formal topic & your bound to run into other anglers that offend easily. Just be patient with them & remember it takes all kinds to make a world!!