Run-Ons are a specific kind of writing, since they have special rules and different etiquette. Here, it is not you writing your story (or if in DIE you and a partner writing your fight), but a series of different people with different styles, ideas, plans and wishes that write a (hopefully) coherent story, starting at a joint path, and often creating some side goals. Usually, there will be one or two intro posts from whoever starts the run-on, stating the rules that apply to this specific run-on, and giving an introduction on the run-on, usually starting/mentioning some special situation that needs to be solved, or another quest to accomplish. Heed them, and try to follow them. Now we will go over the main aspects, just like with the normal writing above, but you should keep in mind that unless mentioned otherwise, everything mentioned above counts in this as well!

• Rules/Intros: The initiator of the run-on usually posts specific rules on how the goal should be reached or what special conditions need to be considered during the writing. This is the attempt to prevent ten people from start ten different quests and involving the others in ten different situations. That is bad style. If you have a really good idea, you can start a side-quest, or even better, some specific quest that will allow all participants to reach the big quest in a specific way. Here, though, the rules mentioned by the initiatior still apply!
  
• No Godmoding: Here, it is really important:
  DON'T FREAKIN' GODMODE !
  Unless you have contacted the other person and agree on something, don't write what someone else does. Especially do not have them act in a way that is completely contrary to how they behaved so far. That simply looks bad, and usually you annoy the others with it. The best way is to talk with them either via mail or IRC and decide together how the interaction goes. A good way is to play through conversations as well, that way things look more realistic, noone is annoyed and the run-on can be brought along nicely. This also concerns the non-player-characters someone else brought in. Using them is bad style, unless whoever brought them in allowed you to do so...and even if so, don't have them act in some strange way or contrary to how they acted before. Some mercenary your run-on partner has hired will not go and let himself be killed for you over some bad joke or alike...unless he was brainwashed.
  
• Post Length: Important...you write posts, not complete books. Keep your posts to what you consider the optimal length, and what others consider readable. There is no pre-set length for that, experiment and find it out. But important here is, do not finish the complete quest in one post. Leave others the possibility to participate (and decide) as well. The only situations were longer posts that cover a lot of actions and alike are acceptable, are when someone tries to bring a totally messed up run-on back into a shape that it can be continued. Else, cover only little timeframes, so that others can bring in events you take care of in your post. Leave others a chance to be productive as well!
  
• Different Paths: This was mentioned before. While there usually is one big main quest, it might be a good thing to bring in one or two side-quests, either things that simply get into the way of finishing the main quest, or something that leads to the main quest... but keep it down. Twenty of those sidelines get difficult to read, diminish the fun others have, and lead to chaos usually. A few to keep things interesting, yes... too many so that things get crowded, chaotic and you can't track everything anymore, no.
  
• Find Your Path: Ok, while named almost like the point right above, this is about you finding what your character wants to do/achieve in the run-on - how you keep yourself busy and entertained. Try to partake in the main story, perhaps in one or two side-quests, but respect the visible intention of those side-quests! For example, as a Sith, do not start to bring in thousands of starfighters and capital ships attacking your folks while others try to bring up some story inside your own capital ships, or on some planet, just because you think it is time for your character to show off his supreme flying skills. Same counts for Obbies suddenly having to battle hundreds of Jedi in some town where your clan wanted to stay unnoticed... Such events occuring over and over are extremely unlikely, make the run-on look weird, and ruin the fun for others since they need to tidy it up, bring it back on track to the main quest and the good/nice sidequests. You could say a good motto here is "Keep it Simple, Stupid". Your character is following some goal being where he/she is...and as a Dark Jedi, that is most likely something to strengthen your position...so find something! Siths are not always just in their cockpits, Obelisks not always fighting someone and Kraths not always in some library! Respect the plans of others, or try to work with them...but if someone wrote what his/her character was thinking, your character will not know it. Maybe the plans he/she thought might accidently crash, though... be inventive! Oh...and one thing... if a group of the participants hangs around in some place and has trouble, while your group is sitting bored around and drinking tea... ok, at some point the Force might give you a tip, but usually you will not have the hunch to simply go where your buddies are, thinking "Hey, I'm bored, I want to go there just for fun..."

This should cover the main parts of run-ons, and hint at some of the worst errors and mistakes that usually appear on run-ons... of course, the normal EH rules (CoC, AoW, Bylaws) also apply, and bashing other participants/clan members for the joy of it, mobbing and all that, is simply bad style. Your character can have a problem with someone or a certain group, and express it...but stay in character for it, and keep in mind that it is not only YOUR fun and joy, but that others want to have fun in that run-on as well, ok?