1. We all know that you can't control other people's characters, right? Well, it's also proper etiquette to avoid Auto-ing. What is this non-existant word? Generally, if you're trying to move the adventure along like so:
"Well, come on then." Joe stated, as the group made their way to the city. Once there...
...that was auto-ing. This guy basically just forced other people's characters to move without giving them a chance to react accordingly or to help describe the journey or what might be going through their minds. Now, it's not always a bad thing, as this example is rather minor, but things of this nature are generally pretty rude.
2. I hate DragonBall Z. Why? Because it takes 7 episodes for a fight to take place. So, in that line of thinking, for the love of Primus, please don't ridiculously overextend fights to beyond belief. Yes, most RPG's are fantasy worlds, but unless you're doiong a fighting tournament RPG, fights are part of the story, not the whole thing. Fights, like anything else in an RPG, are there to helps hape and flesh out the story, not to slow it down and in soem cases bring it to a screeching halt due to it being overblown. Sure, the FINAL CLIMATIC BATTLE should be properly staged with the correct atmosphere, but if every damn fight int he RPG is one where a single punch takes 3 posts to occur....no. It just kills the atmosphere and drags the RPG down. Also, in a fight, be realistic! I don't care how powerful your character is - no one here is immortal, so if your character is shot by a satellite based laser beam, you're going to get hurt - shrugging it off would just be tasteless, no matter how powerful your character is. Frankly, it's just not fair, and even with the new lax rules, a character who can do that would've never been approved anyway.
3. I also disliked the Hulk movie. Why? Well, maybe because we only got about 30 - 45 minutes of Hulk beating crap up and what seemed like 12 hours of Bruce Banner angsting over his tragic past - blech. Basically, try to stay true to the tone of your RPG. If it's an action adventure, keep it as one - drama is good, but don't suddenly turn it into an intense psychological thriller out of the blue. Ditto for a horror RPG suddenly having wacky, zany Loony Toons-esque comedy. Try and figure out what you want it to be exactly when you submit it, then when you drum up enough intrest, talk to the participants tos ee what everyone thinks of it.
4. In that vein, if you're using established characters, such as ones from Zelda or Transformers, be sure that you stay true to the way they're presented in their respective original game/show/move/whatever. While the depth of certain characters is debatable, and certainly interpretation is open to all, don't get way off base. Squall Leonhart, for example, isn't going to be a happy go lucky crackpot who hugs everyone, whether you place the RPG before or after the events of Final Fantasy VIII. Subsequently, nothing in any of the games ever displays Zelda as being a crazed sexpot either, so that's not a good idea either. This, of course, also goes to the worlds themselves - unless you pull a Batman Beyond and place it in the future, Hyrule is not a place filled with technology and flying cars. Granted, if you did that, it would probably turn out more like Loonatics Unleashed then BB, but I digress. Be respectful of the original media, and people will probably mroe likely to join in.
5. Here's a big one - if you plan to do something big and huge in the RPG like blowing up an entire city or killing a major NPC, it's a good idea to make sure everyone is good with the idea. It's one thing if you made up a city and explain after the fact that it was destroyed or make it up for the sole purpose of destroying it, but it's quite another just to blow one up out of the blue. Other people might have their own plans for it, and you would've just squashed them with that act. This is especially important if you're RP'ing in a world shared by other RPG's - if you blow up Kakariko Village in your RPG, what happens to the happy family eating supper in the village in another? So yeah, be careful.
Delphi, DL, Laz, or Chik, anything to add?