As I'm sure you all know, PTCGO is filled with 11 year olds who don't know shit about much anything, really. Quite frankly, the in-game chat/trading system is total shit too - so here's this.
>Post what cards you're looking for, and a picture of the card(s). Be specific - "Dragonite" is unnaceptable, however "Roaring Skies Dragonite with Mach Press" is acceptable. Use abbreviations if you wish (Primal Clash: PC, Secret Rare: SR, Plasma Freeze: PFZ, Looking For: LF, For Trade: FT)
>Post what you're willing to give for said cards. Be vague, this will help you find a match. If you say "LF Aromatisse, FT Aegislash" you're less likely to find a match than saying "LF Aromatisse, FT various holo-rares, PC packs, EX's and supporters". If you want to be specific then be logical as well, follow common pricing rules.
>Post your in-game name so that other players may contact you to trade and hash out specifics. Important: It is advised that you change your Pokemon website login from your TCGO player ID just in case your account could be hacked. Someone harassing you? Block them.
>Don't post what you already have, post what you want to have. No "hurr durr muh binder is up send offers", no "omg who wants this fucking kickass weedle like damn send offers", no "thunderous-ex for 37 RS packs"
>Don't post asking for price checks. You have internet access, look it up. People here will probably lie to you anyway.
>Auctions are the ONLY exception to the posting-what-you-have rule. Rules for auctions: Post what you're auctioning off. Set a time limit - "Auction ends in 2 hours, 6:00pm EST" - and once that limit has been met, call off the auction and make the trade. If you're the auctioneer, regularly check the thread and periodically post what you consider the highest bid. For instance, if your offer ends in 5 hours, post "Current highest bid: ____" every 30 minutes or so. Also post the remaining time in the auction. It's advised you use a tripcode to verify you're the auctioneer.