The following is taken directly from GD.

General Discussion In A Nutshell.
Being the core tenet of the General Discussion forum, distilled down to a single explanatory sentence.

The golden rule when making threads in the General Discussion forum:

To be appropriate to General Discussion, a thread must have discussable content on a topic that doesn't already have a forum or subforum dedicated to it.

Hence the two parts of the forum name:

General being stuff that doesn't already have a forum or subforum dedicated to it.
Discussion being discussable content.

It's not rocket science.

What We Like To See (and What We Don't).
Being a concise summary of what makes us happy and what makes us unhappy.

YES!
Discussable content - Here in GD, we like discussions. Topics that people can talk about and share their opinions on. Shocking, but true.
Stuff that doesn't belong elsewhere - If a thread's on a topic that's already got a forum devoted to it, it goes there instead. Aside from that, any subject matter goes (within the bounds of the Terms of Service).
Respect for others - In GD, as on the rest of GAIA Online, we like to foster an atmosphere of civility, tolerance, and community spirit. Even if you disagree with someone's point of view, please remember there's still a real person behind that avatar, and conduct yourself with an appropriate level of politeness and respect.

NO!
Flaming - If you see a misplaced thread, report it to a moderator. Posting "stfu n00b" or whatever does nothing to help get the thread moved to the right place. Flaming is against the Terms of Service, and can get you warned or banned.
Bumping - If your thread's falling to the bottom of the page and you want to knock it up to the top again, don't just bump. Make a post that adds to the content of the thread or elaborates on the discussion at hand.
Spamming - We do not like your pointless spam, we do not like it Sam I Am. We do not think "bump for gold!!!!" rocks - that crap goes in the Chatterbox.
Begging - If you want gold, either bump 'til you drop in the Chatterbox, or scoot on over to the Charity/Quests subforum. Asking for stuff here will get you nothing but scorn.
Advertising - If you want to publicise your website, auction, lottery or quest, put a link in your sig. Don't post a thread about it in GD. Advertising = spamming, and can get you warned or banned.
White text/Unreadably tiny text - It's not funny, it's not clever. Text which is white (and thus invisible against the page background) or too tiny to read with the naked eye will be treated as if it is not there. As such, threads which do not have any visible discussion will be sent to the Recycle Bin.
Misleading titles - Titles what don't match the discussion are tricksy and false, precious, and gets put in the Chatterbox.