Taking advantage of Inquiring Posters
This is where someone posts "someone offered ____ on my ___" Is it a good deal? If it's pure neopoints, that's the easiest. If you think it's still a good deal, even if you offer more, then go offer more. Don't make a post telling them it's a good or bad deal, just offer more.
Plus, generally they might say is 5k good for my item (worth 15k)? And everyone will say "no". In the mean time you have offered 10k. The person will post a response in the original board "how about 10k?". At this point, no one is paying attention to that board anymore, cause they answered the question. They won't get a response, so they might either withdraw the lot, or may even take your offer.
The way to do that fast is similar to the Being the first in the shop of a Buyable Unbuyable. However, instead of having a blank shop though, you have a blank trades, and do the exact same method. The link to a blank trades is:
http://www.neopets.com/island/tradingpost.phtml?type=browse&criteria=owner&search_string=