IMPORTANT NOTE: This is by no means a perfect list. This is a basic list of things that should be considered when roleplaying (RPing) with other people. The most important thing to remember is to be considerate of the people you are RPing with.
1. Read the rules specific to the RP and ask questions if need be. Most RPers are happy to answer your questions.
2. Ask permission before joining an RP that has already started.
3. If you are running an RP, be sure to be reasonable with your requirements. For example: do not limit the amount of characters people can have unreasonably, and remember: RPs are fun because no one knows what is going to happen next, since other writers can be unpredictable. Take away that element, and you might as well write by yourself.
4. Make sure to find the limits of the people you write with. Some people are uncomfortable with certain types of scenarios. Usual triggers may include, but are not limited to: abuse, inordinate amounts of violence, sex scenes, sexual assault, children and/or animals being harmed, et cetera. Remember, we are all here to have fun, not to make each other uncomfortable. If rules about the above are not listed in the RP rules, then just use your own judgment to make sure you are considerate to your fellow roleplayers.
5. Do not take control of anyone else’s characters. You do not decide how that character reacts to that situation, that character’s writer does.
6. Do not ignore other RPers. If your character goes off on a scouting mission or something and needs a scene to describe that, feel free, but the entire point of an RP is to interact with the others, so that everyone can have fun and improve their skills.
7. Be respectful of other RPers. Remember, they are people too. Not just usernames. They have the right to leave the RP at any point if it makes them uncomfortable, or simply does not meet their incoming expectations. RPs can be spontaneous and unpredictable. That’s half the fun.