Can't speak for all of Fakku but saw where you asked about IB.
So let me lay down what we typically want and don't want in IB.
Don't:
Threads that focus on Youtube videos - we can go to youtube at any point and to watch videos. Short and simple videos or videos that are just outlandishly funny are OK. Majority of the time though, people post videos that are either old, overused, immature, or (my personal favorite) douchebag vlog videos.
Generic Reaction Faces And Replies - this is a hentai/anime site, get creative with your reaction faces. When a new user is replying with a "WTF" reaction face they usually use something like this.
When you should use something like this.
99/100 will think the latter is funnier.
New Users Making New Threads - Majority of the time new users make threads discussing topics that have already long been discussed E.G. "rep threads" or "Do you fap everyday" threads or something very similar. Just don't make new threads period as a new user. When we see new threads and an unfamiliar name beside it, we usually assume "shit thread". Also, don't act like you know everybody right off the bat. Face the facts, we don't know you, don't expect us to be your best friends right away.
Being Flamboyant: Don't spam threads with stupid shit (E.G. Ponies) and keep your opinions to yourselves. Nobody cares about them majority of the time and especially not when you're new.
Being Butthurt: A sure fire way to bring the shit storm upon yourself is to get butthurt over one or two comments. Just take your licks and ignore them. Getting upset only makes us laugh that much more at you. Also understand, hardly anything is taken seriously in IB.
Do:
Lurk - Lurk around to figure out how things work. Figure out which users you like or don't like so you know who to talk to or understand what sort of personality they've got. As just a front, we come off as asshole to start with but everyone's different. You might find its easier to talk to fellow new users or users that have only been on Fakku for several months rather than the older "Elders."
Post In Existing Threads - Goes with "not making new threads". Just post in threads that already exist. Make a name for yourself that way.
Use Proper Grammar - Fun fact, you can highlight a word and you can spell check it. If you use shitty I.E. though, you've still got vast knowledge of the internet at your fingertips to make sure a word is spelled correctly.
I've ranted long enough. Don't make rep threads again and don't try so hard, you'll only fail. Of course these guidelines mainly apply to IB. Elsewhere they don't really apply.