The phrase "Rules as Written" has come up a lot on these boards,and sometimes it's caused a certain amount of consternation. To help alleviate the problem, I'm going to discuss RAW and several other terms, and how they apply to discussions here on the boards.
First off, let's go into terminology.
Rules as written are just that: the rules as they are written down in the books (and corrected in the errata). It is generally assumed to include all official 3.5 Dungeons and Dragons books. Keep in mind that the FAQ is only meant to clarify the rules. If it contradicts the rules, it is technically wrong (though the ruling may still be the one you should use; more on that later).
RAI stands for the rules as intended. This is a tricky term, since you can never be sure exactly what the designers meant, unless they actually come out and say so. However, it can be useful to look at probable intent when looking at a tricky ruling, especially when something can be interpreted several ways, or it appears it was misworded.
Rule zero is the term used for a DM's ability to interpret and change the rules as he or she sees fit. This is spelled out in the DMG (pages 6 and 14), and it's a good thing, too, since you can't always wait for errata to fix the mistakes.
House rules spring from rule zero. These are rulings by the DM (or set of DMs) that are carried from situation to situation. In a group with several DMs, they may either have a set of house rules everyone follows, or each DM may have their own, personal set.
These are pretty basic, and I think most people know the terms well enough already, but I want to be absolutely clear.
Now, the problems people come into occur when it's unclear when someone is talking about the RAW, the RAI, or their own personal house rules. Someone will ask, "Is a monk proficient with unarmed strikes?" Two people say yes, one person says no. Two pages later, you find that one person means that the rules clearly intended for the monk to be proficient, one person meant that they always give monks proficiency with unarmed strikes, and the third was simply quoting the RAW. Then they argue for another two pages, because frankly we're a bunch of nerds here, and we like to argue.
Quite a problem. What can we do to keep this confusion out of the discussion? Let's talk about when each is appropriate.
Most rules discussions should stem from the RAW. This is simply because the RAW is the common framework we're all working from. Not everyone bans polymorph. Not everyone gives sorcerers eschew materials. Not everyone bans natural spell. Not everyone allows you to swing two weapons as a standard action. If someone is asking what the rules say, disregard your house rules, at least until their initial questions have been answered.
Now, sometimes a rule has two possible correct interpretations. For example, Southern Magician could potentially qualify a sorcerer for mystic theurge. However, this is almost certainly not what the designers intended. Here you want to talk about the RAI. This is also helpful when something appears to have been misworded, or left out, like the aforementioned monk's proficiency. Sometimes, they screw up, and it's best to try and figure out what they meant to say. Sure, you can't be sure you're interpreting it right, but it's a good place to start.
Rule zero and house rules should be brought up when you're trying to fix rules that don't work the way you want. For example, drowning. The drowning rules, as written, are highly abusable/unworkable. They shouldn't be used as written. So, you can discuss what your house rules are for that situation. Remind newer DMs of rule zero, so they won't be afraid to change a rule that doesn't work.
Now that we've gone over when each is appropriate, how can we make it clear which is which in our posts?
I think the key here is the difference between "is" and "should be." The RAW is what is, what something does. When you say "the outsider type gives you proficiency with all martial weapons," people are going to assume that you're talking about the RAW. If you say, "Extra spell shouldn't give you spells outside of your class list," they'll assume you're talking about RAI, or possibly house rules. Unfortunately, many people will use "is" and "does" when talking about their house rules or the RAI, and then get upset when someone corrects them.
When you want to talk about the game as you think it ought to be played, make it clear. Don't just say, "this is how it works," and expect people to pick up on the fact that it's just your interpretation. Say, "this is how we ruled it in our group," or "I think it should work this way."
Conversely, when you bring up the RAW, keep it clear that you're only talking about what the rules say. Let people know that you are not saying they need to run their games that way. Otherwise, they may think you're telling them how to run their game.
And for the love of Gygax, be clear on what's a house rule and what's the RAW. I've seen a lot of people defending the RAW with things like, "Clerics aren't overpowered if you have their gods take away their spells," or "Druids can't turn into any animal they haven't dissected and made a DC 25 Intelligence check to show they're familiar with the creature." These are house rules. They may be implied by the rules in some way, but they are not, in fact, part of the RAW. I see a lot of people who are probably good DMs. They make a lot of rulings and house rules that sound like they make the game fun for their players. But then they'll tell you until they're blue in the face that everything they do is purely by the rules as written. They'll lay out a list of house rules that would make Monte Cook blush, and then say that the rules are balanced. The rules are balanced, hallelujah! Sure, if you change the rules.
So, let's try and understand each other better, so we can spend less time arguing over who's talking about what, and more time arguing important things, like monkeys. And ninjas. And monkey ninjas.
Hold on, I've got a new campaign idea. Might need some house rules, though...