Aaah the NeoPets Trading Post. For some it's a place to trade an orn for a bri, for others a way to get rid of a bunch of junky items for hopefully 100 nps but still for others another way to make alot of nps FAST. Here's some observations and some tips to score yourself some profit making lots.
As you know you the idea is to buy low sell for a profit and the trading post is no exception. Hunt for the bargain lots they are out there, you just have to have alittle patience like fishing but you'll find them they are out there.
Make offers on lots that have sellable items like paint brushes, codestones, dubloons, nerkmids and especially map pieces. Species weapons, petpets, food, plushies items like that are alittle tougher to sell right away so unless you find an amazing deal, have a mall or you don't mind the items sitting in your shop for awhile I generally avoid them.
You found a lot and you'd like to make an offer. Make sure you know what the items are worth before making any offer at the trading post. Check with the NeoPets Shop Wiz on every item, this is a must! You don't want to end up paying more than what they are worth at the NeoPets Shop Wiz. For unbuyables do a browse check of the item at the Trading Post to see what other people are asking as well as the rechecking the NeoPets Shop Wiz, you never know someone may say it's an unbuyable but that's not necessarily true, or it may very well be an unbuyable but someone is selling it for under 100k.. Good Score!
Which brings us to the Wishlist. Everyone has em' so always read it over but take it with a grain of salt. Avoid the wishlists that say FREE or 1 nps. 99% of the time they don't mean that they are only doing that to get attention to their lots and will waste your time. Also avoid lots where they are asking for a huge amount of nps that isn't worth the lot. They generally won't accept, you can try offering but you'll most likely get rejected. They are like you trying to make a profit hoping somone will just take their asking price in the wishlist as what the lot is actually worth. If you see a wishlist stating "I know what the lot is worth" you'll have a pretty tough time making much profit off them. Again you can try it but generally they are the ones wanting more than what the item is worth. I always say if you want the item exactly what it's worth then stick it in your NeoPets SHOP!
Hmm what to offer. This is a personal style that I feel you'll get better at honing in the more times you use the Trading Post. What I mean is you don't want to be greedy and offer a crazy low amount and get laughed at or worse called a noob but you also don't want to rip yourself off defeats the purpose. Again the idea is to make some profit off these lots, so depending on what is offered in the lot I try to first round off what the lot is worth, then take off around 5k off smaller lots and maybe up to 10k and up for bigger lots such as unbuyables. The more NeoPets items in the lot the better the chance you can get away with skimming off abit more nps. As well if the lot is expensive some people are desperate and need the nps fast and are willing to knock off 10k, 20k or more. Haggle if you want but be nice about it, when you make your offer always leave abit of room for a haggle otherwise the lot is no longer worth your while. Remember your haggling is dipping into your profit. Let the other person do the talking and if they say oh somebody else has bid higher than you so you have to beat them, then you tell them they better go for the other offer because you aren't matching it. 9 times out of 10 they are bluffing to get you to bid higher. Its a panic tactic and you aren't falling for it. After a few minutes they 'll either close the lot or most likely accept your offer. Congrats!
The scams. There are tons out there so watch out. Avoid lots with a junky item promising to tell you where the faerie cave is if you bid a codestone or faerie. There is no faerie cave. Anyone making promises of secrets or anything far fetched are just trying to scam you. Avoid lots with urls in the wishlists saying how you can make millions of nps. Those are fake logins and generators to get your password. Avoid lots where people pretend the item is some hidden tower item like the Earth Faerie Leaves: Hidden Tower Item, Golden Ivy Leaves: just under 2k. One of the latest scams is the switcheroo. You see an Electric Blue Paint Brush and they are asking for only 70k wow you think thats a profit so you offer 70k. You then get a neomail from the person saying "I got alot offers of the same amount so to be fair I'm going to close the lot and the first person to offer again wins it". They quickly close the lot and put it back up only this time it's a regular blue paint brush and not the electric blue but you are so excited and you want that brush that you quickly offer without taking that split second to double check the paint brush and they quickly accept Nooooo. I've seen the scam using a shadow paint brush switched to a stone paint brush and a battle potato switched to a regular potato. BE CAREFUL
Have fun at the NeoPets Trading Post and remember one Neopian's junk is another Neopian's treasure!