mind your manners
A bad encounter on the river with other anglers can ruin the whole experience. However, by following a few common sense rules those less-than-desirable interactions can be eliminated, or at least de-fused. In the end, it all boils down to common sense.
Don't crowd others that are already in a spot. Give them room and don't encroach on their piece of water.
When in doubt, ask. Talk to others. If you approach an angler, ask them which way they are working - up or down? If they're working upstream, ask if they mind you working downstream. If they say they're working downstream, ask if they mind you jumping ahead and work up.
An angler working upstream always has the right of way to a person working downstream. If you happen to be working downriver and come upon an angler working up, take a wide berth as you go around, and resume fishing once below the other angler.
A lot of the questionable acts seen on the river are simply due to a lack of knowledge. If you feel like somebody has done something wrong, don't yell at them, flip them off, or get into an argument. If you can politely let them know, they'll be smarter, you'll feel better, and a future bad encounter will likely be avoided.
Don't camp out! If you aren't catching anything, move on to find more water. Common courtesy dictates share the river with others. You don’t own the river or the run.
Follow the rules and regulations for that river (e.g., 2 fly rule on the San Juan Quality Waters) and don't leave trash.
Sources: fieldandstream.com; troutsflyfishing.com