Share our tricks? What, so everyone else can take my profits? Naw, I'm just kidding. I'll make a little guide on how to start, if you have never used the market to make money. If there is anything that I do not cover, let me know and I'll share my strategy with you.
1. Graphs
You know that "show graphs" button? Use it. Unless an item is older than one year, or has been introduced a day or two ago, it will let you know how old an item is, and give you a general idea of what the current going price is. Some tips:
~~New Items: Anything that has data for less than 1/3 of the 'month' graph is new, and will behave in a calculatable manner. 19/20 times an item will begin at some absurdly high price, like 80-200k, then plummet to about 1/4 of that by the end a day or two. Do not buy an item when it is at such a high price! it will settle down after a three or so days, at which point you will want to buy. The easiest way to determine when to buy a very new item is to look at the slope/curve of the graph: it will begin very steep, then level out slowly as the days pass. You will want to buy when the angle is around [(3 * pi ) / 4] radians, as it is at this point that the price will vary greatly within a day, yet retain the average you see on the graph. Buy low during this time, and sell high, preferably promptly. If you cannot turn your purchase around within a day, consider selling it for slightly less than you purchased it for, unless you don't mind waiting (and hoping) that the price will go back up in the month or however long it takes until it is no longer available for purchase from the cash shop. You can get away with this strategy until about five or six days after the item has come out, but I would not push my luck- try and do all your buying and selling at the middle of the curve, not at either end.
~~Old Items: These will not vary in price as much as new items, but with patience or a good buy, these will return about 6-10% profit. I do not have any rules beyond what my digestive tract tells me on this, but I do have a few pointers: If the price is low in the current month, watch for good buys (about a 6-10% difference in price from the average), but don't sell them yet. Wait until later in the month, or until the next month, as the price will likely go up by another 10% or so, if it is actually a low monthly price you buy it at. I have not had much success in looking at the yearly graph and predicting long-range price changes for older items, but it is always good to check, and see whether your current month is extraordinary or not. Old items have a lower chance of offering a good buy if the price is higher during the current month, so I advise against buying at that time.
2. Rules of Thumb
Before you think about buying, use your common sense. You aren't sure or feel uneasy about a purchase, don't buy it.
~~Buy Low, Sell High: I cannot put it any more simply than that. But if you can't sell high, sell at the same price. Ex: You buy a shirt at 200, then the price goes down and you manage to get rid of it for 100. You are left with 100, meaning that the next item you buy must DOUBLE in price for you to simply get back to where you were before. This is, needless to say, unlikely.
~~Bulk Items: These should be strayed away from, for two reasons: one, you will spend a lot of money at a single price, so if the price changes, you will be out by much more money than if had bought only a few. Secondly, bulk items are not listed near the bottom of the list, no matter how good the ratio of items to cost is, meaning that they are less likely to be seen by your customer. Conversely, few people look at bulk items, so if you do see a really good deal in a stable market, you can buy it, then split it into smaller portions that will be nearer to the front page or bottom of the list.
~~What to buy: Don't buy things that you would not wear or use yourself. If you get stuck with something ugly that you will never wear, chances are that you will sell it back, even if you have to take a loss. Buying something you like means that you can handle holding on to your item until the price returns to something more favorable. Also, I am a fan of buying Collectibles, but not the ones for the current month. The ones for the current month will drop in price after about 2-3 months, at which point you might consider buying them and saving them for a few more months. I do not like this approach, because it renders your money useless for long periods of time. If you have lots of money, feel free to make long term investments. The rest of us who keep about 30-40k worth of items for buying/selling will just try to get them off our hands as quickly as possible. Old Collectibles are generally a good buy, as long as you follow the rules above.
~~Duplicates: If you see many (more than 2 or 3) of the same item at a price lower than the average price given for today, don't buy. The price is going down, and even if they look like a good buy, you will probably just end up crying as your good buys become the average price, then too expensive. Also, it is usually unlikely that you will be able to wear/use duplicates of an item, so if you follow the above rule, you will cut down on losses from this situation anyway.
~~Really Expensive Items (over 150k): These are generally not a good buy- the price will not change within a month any amount greater than about 5%, what I deem a poor return for the risk. If you are good at spotting long-term trends, I'll let you risk your money with these. Also, if you are in possession (and selling) of one of these items, it is likely that people might ask you to trade them the item, or lower your price, etc. because the prices do not change much. I do not suggest trading these for other items or a lowered price- if someone is offering another item, they probably know it is time to get rid of that item before the price gets much lower.
~~More About Graphs: Along with the graph for average yearly/monthly price, there is a graph for average yearly/monthly buys. I do not suggest attempting to resell items that have purchase peaks of around 15 or lower. If nobody buys the item, it will be easy for someone else to undercut you and take one of the few sales for that day. If you are intent on selling one of these items, I suggest making yours the cheapest on the list, and checking to see if you have been undercut every few hours, which leads into my next point:
~~How Much To Sell For: Okay, this is where you might read my advice and question whether I know what I am talking about or not. You'll just have to trust my judgment on this one. Do not sell your item for the lowest price. If you can avoid it, do not undercut. Undercutting destroys the market, and makes your chances of making money less. If you are really after a very quick sell, follow these guidelines:
~~~~Price yours at the same price as the lowest one. Don't undercut, as it will only harm your source of money in the long run, even if you make a quick profit in the short run.
~~~~Sell items that have high buy rates, generally anything with peaks greater than 75, and lots of them. Items with an average buy rate of around 150-250 are even better.
~~~~Don't have an obnoxious name or shop description. I have noticed that people with a single item for a low price often have many items for lower prices, but people won't be interested in looking at your store or other items if your name is xXxSh0rttSkirttxXx (that was made up, not a real user I have encountered).
~~How Much To Buy For: Again, anything that is 6-10% less than the current market price is a good buy, unless there are many below the average. I suggest buying items that cost around 10k, because these will vary the most in price percentage-wise, giving you the greatest percent profit, at a price that is within the range of anyone who has played for about two weeks. If you are still getting on your feet, or just do not have enough time to devote to puzzles to make seed money, I suggest buying below 1k. Things between 10-1k frequently mislead you with average prices, change in an unprofitable manner, or do not change at all, since most items of this price are available in stores.
3. FAQ
Ask and you shall receive (answers).