Now the best advice is 'don't', but if you must here are the things to look out for.
1) On first posting, you will be accused of being 'squiff', 'git', 'mavis' or 'Lisa'. You will routinely be abused and insulted, and anything you post dismissed as 'attention seeking'. Don't take it personally, it's quite normal.
2) You will find that most posters on the board come from India, Singapore, and Afghanistan. This is because nearly everyone who posts is banned and use multiple IDs which are easiest to set up from those countries, as only a hotmail email addy, and no credit card, are required. False details are of course de riguer.
3) You will at first be pleasantly surprised to see that most posters are as new as you, with zero feedback. Actually they aren't, but if you post in your trading account you will be 'AW'd', that is auction-wrecked. Somebody will bid on all your auctions just to leave you negative feedback, or if you just buy, look up what you buy and outbid you just to annoy you. Again, don't take this personally, it's quite normal.
4) You will quickly notice that the moderation of the board, run by Liveworld, is a little..erm.. strange. That is, abusive posts left in IDs, often taking the form of other posters' personal details such as phone numbers, adresses etc, are left for ages, but if you post to complain your post will be instantly removed, and you may well be banned. This, it is generally believed, is because some of the 'moderators' are also the people posting personal details and abuse.
5) You may wonder why ebay do not do something about this. This is because the EBAY person in charge, who goes under the pseudonym of 'Henry Nutford', is a complete idiot. He is now too scared to post himself as most posters loathe him, he has posted threads inviting comments about the board only to 'block' them when he doesnt like the comments, and on occasion has had to pull his own post because he has libelled a poster! In any case, Ebay have no control over the boards as it is impossible to ban posters whatever they do, a new ID taking experts just seconds to create.
6) After a while of posting, even if you just say 'hello' a few times, you will offend some posters. This is because a frightening number are mentally ill, alcoholics, or retarded. You will know you have offended them because they will find out your persnal details as above - address, phone number, name, family names etc - and post them on the board, abuse you, and if they really don't like you send you dog pooh through the post, or abusive letters to your family. You can of course report this to ebay, who will ignore you.
7) You will also be drawn into the family lives of certain people, such as 'Lisa', 'Mark' and 'Squiff'. You may find these alternately incredulous, or mundane to the point of delirium. You will be expected to post what you have had for breakfast, lunch and dinner, pictures of your pets, and detauils of your latest knitting project. Additiona information, such as how many sugars you have in your tea, is always welcome. If you would like a serious debate about any topic by all means post a thread on it, but do not expect anyone to understand if you use words over 5 letters.
8) One of the highlights of the board is 'sniping'. No, this is not winning an item by a late bid, it is simply being the 50th, 69th (don't ask), 100th etc person to post on a thread. This is considered a great achievement, and indeed for some posters it probably is, and will be greeted with posts of 'good snipe', 'well done', etc. If you don't want to join in the excitement that's ok, but you will not be allowed into the 'clique', that is, everyone will ignore you.
9) Humour is not allowed on the board, in any form, and any post containing it will be pulled by Liveworld. However to make it up for this it is customary to post 'PMSL', (I have urinated myself due to mirth) after any post which is not reporting a death in the family or similar disaster. After such more serious posts, 'LOL', (I am making an inane chortling sound) is more appropriate. If genuine humour should briefly appear, 'ROFLMAO', (My body is separating due to the strains of excess mirth, and I am having a fit on the floor) is posted. It should be noted that while body separation is not in fact normal, posters having seizures or fits due to severe mental conditions probably is.
10) Finally, you may acquire the status of a 'Respected Poster'. This you do by stating you are one, and getting into somebody called 'Ribbon''s good books. This in turn is achieved by conversing with as many posters as possible on MSN Messenger, ideally in several identities, and sending all the private conversations to as many other posters as possible but especially Ribbon and 'Cal'. Conversations which 'slag off' people who think they are your board friends are particularly prized in this respect. Keeping files of every other poster, and all details about them, is also good board etiquette as it allows you to swap information and supply the 'trolls', (regular 'nice' posters, who also post insults etc to their board 'friends' under other IDs.
So welcome to the Nags Head. Please enjoy your stay there, however brief, and try not to get short utinating through excessive mirth as it can mess your mouse/keybord up. Happy posting...