Selling your items is a quick and painless process (and rather rewarding) if you're advertising in the right place. You can make a lot of money in pre-searing selling average weapons but you have to know where to go.
Warrior's likely gravitate towards warrior quests and trainers so head off to Barradin's Estate to sell that 9-11 sword. Casting classes are everywhere but Ascalon City is the most populated. Foible's Fair is a decent spot to target those wily casters as well.
Post-Searing, class lines are blurred and then it becomes a matter of knowing skill level and wealth. Selling that Rare Axe of Awesomeness in Sardelac Sanitarium is a bad idea. People don't have the money to give you what you think it's worth and more than likely don't come close to the requirements. Similarly, people in Lion's Arch will laugh at you if you advertise that 7-10 Rinn Blade.
2. Know the value
Some of the stupidest stories people have recounted deal with ignorance. Know the value of everything in your inventory. A good rule of thumb is 10 times what the merchant would pay you for it (obviously there are exceptions).
A lot of the value is based on the market you're in. As I mentioned above, a 9-11 sword will fetch you a decent price in pre-searing. You'd have to pay people in Lion's Arch to take the same sword off of your hands. Most of the drops you get in upper levels can be worth a lot to people starting out if the item requirements aren't too steep. If you have the time, zip on back for some quick gold.
In the end, it's worth what it sells for. You may not think that Fur is worth 1000 gold but I've sold plenty at that price. Selling for less is just stupidity. If you don't know the value of something, aim high and let the market prove you wrong. Friends are not made on the trade channels, they're made in missions. If you want to be charitable, sell low to your guildmates--they'll appreciate it whereas the public will forget you 1 minute after the deal.
3. Irritating vs. Effective
The single most damaging aspect to Guild Wars' economy is the Caps Lock key. So many people have been turned off to trading because they see the spam that occurs on the trade channel. Many of us advocated for an auction house that would have alleviated this issue but he we are -- complain about it elsewhere.
Capitalized letters and symbols should be used sparingly. Acronyms and abbreviations are fine but again, understand your market. You might throw around PM, WTS, DF and Req as though it's your native language but there are plenty of people new to this game that have no idea what you're talking about. Usually these new people are the exact audience you're trying to get a great deal off of -- do yourselves a favor and make it easy for people to respond to you.
Do not post the full stats of rare items or other long modifiers. These just clutter the channel. Bonuses and modifiers should be thoughtfully abbreviated (if possible) or just listed as "3 bonuses, take a look". Bonuses and modifiers don't generate interest as much as Rare, Purple or plain, hard numbers. Definitely don't post requirements -- that's for your customer to worry/ask about. All of this should go into how you quote your price.
Selling: Blue DYE, whisper me with offer. Perfect except for one thing, "whisper me with offer". Know the value of what you're selling, mark it up accordingly, then advertise your price. Every time I see "PM me with offers", I offer what the merchant would pay. If someone says it's worth more than that then tell them to sell it for said price and quit cluttering up the trade channel with advertisements for offers.
Do not be scared to quote high prices. Something is worth whatever someone else is willing to pay for it and the only wrong price is the one not specified. You can always negotiate but give a ballpark figure as a starting point. If they're interested they'll tell you and you can go from there. "PM me with offers" turns off more people than it attracts.
To Sum Up:
-Know who you're selling to
-Know the value
-Use capitalization, repetition, acronyms, symbols and abbrev's
sparingly!-Quote a price
"It's worth what you sell it for."
