Originally Posted by
Rhaemond
This. The Price Check Megathread is always a good place to ask but don't trust any price some people might give since sometimes they'll give a really bogus price on an item...
Like Question: "How much does KFMB go for these days?"
Wrong Answer by Toribashian 1: around 200k-300k
Right Answer by Toribashian 2: I just sold mine for 160k. They usually go for 120-160k
So the Price Check Megathread will sometimes be untrustworthy unless you really trust the guy who answered your query.
Alternatively, you can ask around ingame, irc, or PM people especially big game marketers.
Anything that isn't a collectors item or some miscs, not all, should be good things to sell.
I also suggest you buy and sell through PM most of the time, it's more easier and less cluttered.
Lowballing isn't a good thing to do most of the time if you don't want to get your rep tarnished to shit. But yeah as what Alpha said use it as a last resort if you don't know the price so you'll have a bit of leverage when buying stuff.
Well, that's about all the advice I could give I guess. A [B] thread seems cool but I kinda don't like it... A lot of people tend to highball when it comes to the forums but I digress, I might try it also.
PM me or post here if you have any more questions, and why not join us? 
Raiken told me a quite long ago, that one of several way to set a price when buying is to take -1k from the lowest market price.
But how about selling an item, how do i set the price?
My current problem is that i don't know when i am doing a highball or a lowball, since i kinda do that subcounciously due i don't know the 'good' price for the item
and i do want to join, but not now...since i am not a marketeer yet, and all of you people seems experience enough regarding on the markeeting stuff