OK here goes some basic guidelines.
1.
MOST IMPORTANT THING! Don't forget that the tp takes 15% (or more) of every sold item. It costs 5% of the item's sell price to list it and the tp takes a 10% fee when it sells. The (or more) is that if you list something then take it down to re-list it you pay the 5% again; Make sure to factor that in if you have to rel-list an item. To figure out if an item is profitable, there are 2 formulas I use.
(Final sale price I want) x .85 = (How much I get from the sale)
or
(Cost of materials) / .85 = (How much I need to sell it for to break even)
2.
2nd MOST IMPORTANT THING: Patience. Get rich quick only works about 5% of the time. Don't try to get rich quick.
Put in buy orders instead of buying at lowest seller price.
Sell at lowest price instead of selling to highest bidder.
It will take longer to get (or sell) your items, but every copper counts and it is worth it in the long run.
3.
http://www.gw2spidy.com/ Use this site whenever you are trying to evaluate if an item is profitable. You can search for market trends for flipping, crafting cost vs end price, or just see if something is worth buying as is or to wait for the price to come down.
4.
Craft high end items. Get at least one crafting discipline up to max and find the items that will sell for more than the crafting mats. look on spidy's crafting tabs, I.E.
http://www.gw2spidy.com/recipe/3700
Don't just look at the top tier stuff though, there is lots of mid and lower tier stuff that will get you silvers every time you craft.
5.
Craft 2nd level crafting mats. This one is easy, but takes a while. Its a high volume/low profit strategy. Turn ore to ingots, logs to planks, cloth scraps to bolts etc. Just calculate the conversion cost of the items and don't forget the tp cut.
(this one directly answers your question from the first post)
6.
Flipping items. Look on spidy and find trends where items go up and down in a cycle. Day vs night, Weekday vs Weekend, First of the month vs middle of the month, Winter vs Summer. Crafting mats sell for more on the weekends vs tue, wed, thurs, because more people are on during the weekends and want to get their crafting done so they spend gold on the stuff.
7.
Predict markets. Holiday event coming up? buy items that can possibly be used in crafting holiday stuff. Pumpkins spiked for Halloween, chocolate, cookies and milk spiked for Wintersday. Just make sure to not hold on to your speculated items too long. the spike will always correct itself so make your profit and get out.
Don't forget that gem prices spike before and during a holiday event because people don't plan ahead and find out they want some cool gem store items. Buy gems in the off season and sell them during holidays and whenever new stuff is put on the gem store.
8.
Limited time items. Stuff that comes into the market during events that aren't attainable afterwords will go up in price later on, but it may be much, much later. I am still holding onto some Halloween skins that I got for cheap. They should be worth double what I paid but it will take about 6 months of sitting in my bags.
9.
Gamble. I'm not a fan of this, but things like the mystic forge, the new chests that you can buy with random stuff in it, etc. If you can track the numbers of what you buy and what you get, you can have a better chance of coming out ahead. This is why I love spreadsheets. However, if you don't go in fully armed with tons of information you will probably lose money.
10.
Patch notes. Changes in the game always makes room for some profit to be had. When specs change and new stuff is put in the game, there will be reasons to sell (or stop selling) related items. If you read the patch notes you will be able to predict changing trends and jump on while items are cheap. Then when people realize that such and such is the best spec and go buy the items to support that spec you can sell your stockpile for a profit. When they add new recipes that make use of a hardly used item that items price will spike.
Finally, go check out podcasts 9 and 10 (I believe) where I bored Tristan to tears with all my making money stuff. Most of the things I talk about in those make money podcasts still apply and there are tons of good links to get ideas of what to do. Also how fitting is it that this is my 100th post on these forums? Perfect timing for this question imo.
