When in Rome, do as the Romans do. Look at what posts get a bunch of positive ratings versus negative ones, since user feedback is about the only use those little stickers have. Also observe the first five or so pages of a thread to see the reception it gets. If it's positive, imitate. If it's not, well, then don't.
It also helps to read the rules, forum descriptions and any stickied threads in case you somehow don't know to do that. I'm presuming you didn't, considering you posted this thread here.
Pretty much find something you think is funny and just read. And don't necessarily feel the need to just jump in and say something in a thread. Maybe what you have to say isn't new, and doesn't provide any sort of information to the thread.
I think the rule we're all getting to understand at this point is if you aren't having fun, it isn't worth doing it.
1. Understand we are all autist here so don't get pissy when someone gives you shit on the site. I've seen one too many newbies get angry about negative ratings and derailing threads.
2. You can delete your post, only double post if you have to.
3. Find a thread you can contribute to so you can start to learn how the Farms work, then after you've had practice move on to other threads.
4. write your post out, read it, and consider if it adds anything to the conversation if not delete it.
5. limit your initial posting, When you finally get the courage to join in on the fun you want to bring up everything you wanted to talk about while lurking but you shouldn't. Not only will you burn yourself out but you could end up saying something stupid or pissing of kiwis and not realize it till every thread hates you.
6, We use bad words here, especially since the word filter got axed, if you can't stand people calling you a retard, nigger or a faggot get off the site it isn't for you.