1) Don't Tell Us We're Going To Hell.
Seriously, we don't believe in hell so it doesn't frighten us. All it does is make you sound like an intolerant sadist who gets off on the torture and suffering of anyone who disagrees with your beliefs. Imagine if someone said they think that everyone who believes in any god(s) deserves to spend eternity in perpetual pain and fear, that'd probably piss you off too, right?
2) Understand That The Existence of Monkeys DOES NOT Disprove Evolution.
Just stop and think for a second, what is more likely? That hundreds of thousands of scientists, who have trained for years to evaluate information without bias and have access to all the evidence, research and critically robust and peer reviewed studies have somehow failed to notice the existence of monkeys OR that you don't understand how evolution works?
(On a related note, the word "theory" has different uses depending on whether it's being used in a scientific or general sense. In scientific terms "theory" doesn't mean "guess", as it does in general terms, instead it actually means "collection of understood facts supported by masses of evidence", learn this distinction to avoid (a) looking stupid and (b) atheistic mention spam!)
3) Don't Try To Claim That Atheists Are Immoral.
Firstly, PLEASE READ YOUR HOLY TEXTS OF CHOICE! Those books are filled with condoned "immorality". Incest, torture, rape, murder, child abuse, slavery...I could go on and on! Seriously, if you live by the standards set by any holy text then your moral compass is about as reliable as as those crappy little plastic ones you get in cereal boxes and Christmas crackers, it may look like it should work, but relying on it is guaranteed to leave you wandering in the ethical wilderness!
Secondly, statistics, worldwide, have shown that, of all religious demographics, those without a belief in any gods are less likely to divorce and are notibly underrepresented within the prison population.
Basically, if you allow any book that actively encourages you to discriminate against huge swathes of the population to guide your behaviour and how you treat others, you have no moral high ground to stand on and are likely to piss off a lot of people!
(On a related note, don't call us "satanists"! We don't believe in home either, see step 1 for how this makes you look!)
4) Don't Try To Force Your Beliefs Us.
We don't give a damn what you choose to believe. It is your right to believe anything you wish. However, that right doesn't include changing legislation, that affects everyone, to reflect or give undue support to your beliefs.
Neither does that right include trying to convert people to your belief, they have the right to believe whatever they want too!
Nor does that right include having your beliefs treated as facts in any secular establishment. This includes schools, universities, hospitals... in fact, anywhere that isn't a church, temple, synagog, etc!
5) Just Don't Be A Dick!
This is probably the most important one. If you're going to say something that sweepingly prejudiced, grossly offensive, startlingly ignorant or just downright stupid, and don't want to be barraged with masses of criticism, well reasoned rebbuttals and abuse then either set your tweets to private, or consider removing yourself from public forums. Otherwise you deserve everything you get!