Welcome to Serebii, friend. A few things you need to be aware of:
1: ALWAYS read the rules. Whether it be of a forum, sub forum, clan, trade shop, or anything else. Rules are important, and the Moderators rightfully take their jobs to heart.
2: Spambots are evil. End of discussion. If you see one, report them. They will usually have a link of some sort in their post, although we have recently had a string of 'newbies' with links in their sig (these were bots, also.). The main telltale about a thread made by a spambot is that it will be a completely nonsensical section. For example, the fake-newbies I mentioned above have been appeared in the 'general Pokemon discussion' section, instead of the newbie lounge, where you correctly posted. (Props to you on that, btw.) You can report spambots by using the 'yield' icon in the upper right hand corner of each post.
3: Posts are good, as long as they aren’t spam. If you read the rules, I believe there's a description of what qualifies as spam there.
4: If you're looking for friends, clans are the best way to go. They'll teach you about competitive battling, help you fill out your Pokedex, and in some cases, even goof off. My own clan, Operation Obliviate, is especially friendly, and we excel at the goofing off part, although we aren’t slouches at competitive battling, either.
5: Don't clutter the forums. If you're going to make a new thread, look around and make sure that there isn't already a thread talking about your topic. Duplicate threads simply get closed by the moderators, and it just makes their jobs more difficult.
Well, I think that covers just about everything. If you have any questions, feel free to shoot me either a VM or PM.
Welcome!
KingOtheStone (Call me Kotsy)
ps: If I left out anything, I'm sure that someone else will post it.
pps: Join Operation Obliviate, especially if you like battling! (Applies to anyone interested)