As I said in my post in Questions and Answers section, this topic of mine would eventually move to Guides and Tutorials section as soon as it's ready, and it's ready now. This guide is based on my prior experience, friends' suggestions, and other members on this forum who have posted comments on my prior post. Thank you all, and especial thanks to ieatpasta, Mephala, BloodyBlade, and washikaba's support.
So here we go.
Section 1: Recognizing scammers<If you are in town>
(1). Strangers who ask to see your sos or offer a good price for your sos are 99% scammers. 
Some people will ask you if you want to sell your sos weapon, or anything for a really good price. for example, they will say: "35mil for your sos weapon." DONT EVER trade with random people through EXCHANGE SYSTEM. if you do want to sell your item, OPEN A STALL INSTEAD, and ask the person to come to buy it in your stall. It's SAFE this way. If they dont come to your stall, guess what, they are scammers. cuz during the exchange, they can change the price to a way lower price than how much your item worth while distract you by make friend proposal, etc.
(2). Don't believe anyone who asks if you want 500mil for free. (Tips from DA_CAT)
Seriously...
(3). Be careful with 1 gold item in the stall and un-open stall. 
scammers can change 1 gold to a big amount while you r buying it from their stalls. so when you do buy stuff from people's stalls, make sure the stalls are open.
(4). Ignore people who are trying to sell you silk. 
500k gold for 250 silk???? you know that you r not lucky enough to get such a good deal.
(5). Never trust anybody who says they can duplicate or plus your items. (Tips from Mephala and washikaba)
I will explain how scammer can duplicate your item later in the ouside the town section.
<If you are outside the town>
(1). Don't trust some of the plvlers. 
Pay every half hour. dont join the pt if everybody is in the same guild. dont join the pt with only 2 or 3 people and you can tell they are related by their names (cuz they are probably togehter to scam you). be careful with people say "no 30mins" (7/10 are scammer from my experience).
(2). Don't open a stall outside the town. 
If you open a stall outside the town (lots the time, scammers will ask you to do it), the weapon you sell can be "duplicate" from a bug in this game. That's why lots scammers say they can copy your items for you, etc. So, what's "duplicate" really means in here?
Ok, after you open a stall outside the town("open" in here means that you click open in stall network), people whoever in your go to your stall will be able to buy your item. After they buy your item, they will get the actual item for how much they paid for. And you, at the same time, will still "have" the item due to the bug of sro. This is the "duplicate". however, the "item" you "have" in your inventory will not be the actually item since you cant trade it, neither drop it. however, for some reason, if it's a equipment, you can actually equip it, but it won't do anything. To be simple, if you sell stuff outside the town, whatever you sell, people who buy it will get the actually item, you will get the fake one. So dont open a stall outside the town.
Here is a video that BloodyBlade found on Youtube that show you how this happens.
http://de.youtube.com/watch?v=AW-zbDjmpPESection 2: Tips to Preventing Scammers1. be really careful when you r in donwhang. 
from my experience, donwhang has the most scammers. dont ever trust anybody here who wants a trade, exchange, etc. if you really think they are serious buyers who offering a good deal, set up a STALL and ask them to come to your stall. if they dont come, haha. they are scammers.
2. be really careful to strangers if you r wearing pimp avatar.

avatar is the easiest way to tell other people that you have silk. so does ability pet. watch out when you have pimp items such as sos too. cuz when scammers know you have silk and plenty gold, you become scammers' main target.
3. when you r not in town, open up the chat window to ALL so you can see whats everybody is talking about especially when you r doing taxi. 
This is a good way to get info about taxi scammers. people who got scammed by the plvler in your area will always say something in the chat such as "....is a scammer." so you will know that you dont wanna take taxi with this scammer guy.
4. join the guild that you trust. 
have you heard about that some guild are scam guild? I heard about it. the whole guild is full with scammers and the purpose of the guild is to scam noobs.
5. dont trust anybody too easily that you dont know in real life. 
some people will make friends with you in game, and earn your trust. and then, guess what. they will scam you. for example, a lv90 guy gave me powerleveling couple times, and he was really nice. one day, he said he could plvl me for 8 hours straight, and asked me to pay him a huge amount of gold. i trusted him. i gave him the gold. a sec later, he got dc. next time when he log on, i asked for my gold. he deleted me from his friends list and blocked me. it's that simple, isnt it? im not telling you to not trust anybody in the game, cuz there are good and nice people. but you never know, right?
Section 3: If you still get scammed.(1) Always remember how much gold you have so at least you know the amount you lose from getting scammed. (Tips from Mirosuke)
(2) Share your experience with your friends and the forums and help us to prevent scammers.
(3) You might think you are stupid, but you are really not.
(4) Learn from the lesson, and be careful next time.
Thank for reading and good luck.
