1. Never, ever, never, ever, ever, ever post a level that you haven't played yourself to make sure it works!
2. Enough with the 'wood' texture. If you're that incapable as a level-maker to pick one of the other default textures then don't post it!
3. Do not, under any circumstances ever again post a level with a hidden maze...it's been done to death!
4. Do not under any circumstances ever again post a level with a pac-man theme. Do I even need to say it.
5. If you want to hex-edit the hell out of of a level so that no one but you and your I.T. buddy have a clue as to what's going on, fine! But when you post it make mention of the fact that you have created a level that in actuality has very little bearing on the parameters of the game.
6. 21 is the maximum number of boxes that you can put in a level that need to be pushed somewhere. I don't care if the generator spits out 5,000. 21 is all we'll push and even that's too many.
7. Unless you have posted somewhere between 500 to 600 levels you are not allowed to make a 3D level. With rare exception, they're annoying.
8. A level with piles of coileys and ghosts that you somehow have to get by with a truck-load of luck is not a level. It's crap.
9. Doing the same level over and over again but with different textures and different names is not allowed. If you can only come up with one idea, so be it. There's no such thing as the 'Greatest Hits of Dexy's Midnight Runners'...'C'mon Eileen' was it!
10. This is not a firm rule but the level should actually come on the screen before you have to do something. Trying to move 'Stinky' 3 seconds after you've turned your computer on is too soon!
11. Mette put a lot of effort into creating a texture's list, use it to acknowledge someone's work. Don't worry about the model list, I find it confusing as well.
12. If you have to make a level that requires lots and lots of tramp work, Qookie can't be the main character. The sound of that character jumping scares me and my cat.
13. Enough with the hidden coin in a false wall!
That's it for now, if I think of something else I'll expand the list.
Have a nice day.

Edit: It seems no.1 was causing too much confusion, it's been changed.