1.) Don't use smilies while IC.
2.) Quality over quantity.
3.) Don't interrupt other RPers.
4.) Respect your fellow players.
5.) Create dynamic characters.
6.) Create dynamic stories.
7.) Develop a profile.
8.) Develop a history.
9.) Justify your actions.
10.) Be aware. Don't skim posts.
11.) Be pro actively aware. Go out and read their profile.
12.) Follow the dramatic progression: Introduction, Conflict, Climax, Resolution.
13.) Be original.
14.) Be inventive and creative.
15.) Intelligent and Imaginative ideas.
16.) Research.
17.) Show, don't tell.
18.) Be descriptive.
19.) Keep an open mind.
20.) Don't force actions on other characters. (This includes forcing damage on them, also called "Auto Hitting)
21.) Don't txt-tlk.
22.) Be concise.
23.) Don't fall in love with your own character.
24.) Always learn.
25.) Use a thesaurus.
26.) Spell check.
27.) Grammar check.
28.) Read over your work.
29.) Re read over your work.
30.) Separate IC and OOC.
31.) If your character dies, take the opportunity to learn.
32.) Read as much as you write.
33.) Don't try to take over someone elses RP
34.) Don't argue with the RP master, this may get you banned from the RP
35.) Don't control other characters without permission.
36.) Just because your the RP master, doesn't give you the right to control everybody's characters whenever, let the players post there characters actions, it can be more fun like that.
37.) Pay attention to the RP specific rules.
38.) Read the first post, it often has who is playing, information about characters and a form to fill in to join
39.) Act maturely, don't say type in dumb actions, like *has sex*.
40.) Don't make a Mary-Stu/Gary-Stu (An around perfect person with no flaws). It's boring if the character doesn't any flaws what so ever.
41.) If you are going to have a god-mod like power in your character, balance it with a flaw (a example would the character has extremely powerful magic though he/she can rarely use it and nearly every attempt to cast ends in failure)
42.) Keep a realistic inventory. If you're character is an Assassin-esque style, don't give them a two-handed axe...
43.) Don't try to force a history on another person's character.
44.) Don't contradict things in your profile (EX: Your character lost his/her arm in X war, he/she should not dual wield).

Far from 101, but if you think of anything else, let me know so I can add it.

Don't try to force a history on another RPer's character.

Added....

Slight disagreement there.

Shouldn't GMs be able to do that?

Depends on the RP, but we aren't really talking about when you're DMing an RP, just RPing in general...

I understand what you mean. It just came to me when I read it

what would be an example of forced history? >.> ive had nini have flash backs for her history in RP, in an RP not surrounding Nini..is that an example of such?

No.

Like, for example, a relation to another character. Such as someone joining and being the niece of a character already in it. *Cough*

Hey! Curse you and your memory!! That was my first time ever RPing

lol nub

Don't spam, even in OOC.

Err, Don't contradict things in your profile (EX: Your character lost his/her arm in X war, he/she should not dual wield).

Makes sense.

...Guilty...

Don't try to control what happens to your character with no good reason (Ex: He process searching for the town of X, After a while of searching he finds it by asking a traveler on the road.)