Well, the only way I can really think of this is to explain it in examples :3

Scenario: You want to buy a Chibi Potion, so you go to the trades and see them priced around 1 mil sP. Now, this looks fine, the prices are ok... but the people selling them /don't/ want you to know that they are buyable in the Millionare Center (MC).

I know, it's hard to know where everything is, or even if it stocks certain places. But if you ever want to know more about an item, just check out Skyotica [aka SubetaDB]. You can search for the item and it will tell you where it restocks, the rarity, the description, and other info if it has it =]

Scenario: Someone tells you to buy an item from the Token Shop, and they'll give you the tokens after you buy it. Make sure you use the trade center to do this! Never give anyone an item and expect to get something in return. NEVER, got it? xP

Scenario: You're innocently talking to someone, when they mention that they just got like 10,231,843,692 sP! All you need to do is give them your password and PIN and they'll go and put some sP in your account. Don't ever believe this! Never ever ever (you understand me? xD) give out your password, PIN, or other personal information :3