This indeed is basic and I think every, or almost every, half-decent RPer will have picked these up or know these already.
However, that doesn\'t mean that this is always done coherently. A lot of times conversations that clearly are OOC aren\'t marked as such. While this might not necessarily be a problem if the content clearly distinguishes it, it still is a matter of principle: getting used to something will help prevent forgetting it when it\'s important.
This brings me right to the point: a clear, consistent designation of OOC is important in cases where the conversation might be IC or OOC. Yes, this is possible, and in fact I had several such an occurances already.
Clearly designating OOC is the only way to ensure that undesignated talk can rightfully be expected / assumed to be IC speech in all cases, which is necessary to not drive RP into the background. \"Mostly\" doesn\'t cut it, it must be \"always\".
As I said, I had several occurances of unclear distinction, and one case went pretty bad with me being rather harsh towards another RPer who happened to be OOC at that time while I was IC; all just because there were some simple brackets missing. Luckily, I eventually noticed my mistake so I was able to clear up the mess, but it shouldn\'t have happened in the first place.
Thus, obviously none of the clueless people will read this, but no RPer would seriously expect their talk to be IC anyway.

So this really is a call to the RPers to strive towards a consistent and consequent designation of OOC talk so things like that occurence won\'t happen.
Maybe a link or inclusion of this would be worthwile on the RP sticky.