A scam should be carried out by a scam artist. They should be articulate and meticulous in their writing. When you say 'I', don't go putting 'we' in your next sentence. Don't reveal the fact that you have accomplices. It won't do them any good. Be creative, come up with something original.
Be discreet when you want to create multiple accounts. Use someone else's birthday. You know that there are 365 other days to choose from including the 29th of February, so why didn't you? You're welcome. Choose another place of residence unless the system decides it for you. If it does, choose another day to create second account BUT ALWAYS remember (I cannot emphasize enough on this) to choose another birthdate.
Don't sell the same thing only a few days apart. Make it a week apart at least so your first post would be overwhelmed by newer posts that people have forgotten about your first post.
Use your own product photographs. At least, those that cannot be traced and not retrieved from Google Sensei. Make sure all images have the same resolution and show the same things (if you're selling a couple of the same item). Avoid putting blurry and clear photographs together; it just makes you look like a bad photographer.
Come up with a believable talltale. Not some essay your younger sibling's friend's brother's cousin's pet hamster's abominable snowman wrote for their English assignment hoping to fail with flying colours. YES, FAIL.
Please find it in your conscience to stop before you take what is not yours. It's not the money alone. It's the trust the person chose to put in you and the belief that you are merely trying to help. Online it may seem easier to deal with the guilt (assuming you have any) since you're taking something from someone you don't know but there's something called IP ADDRESSES.
I still remember the first time I got scammed. I was young. I had saved enough money to buy that autographed McFly DVD off eBay. Paypal wasn't so established yet and I didn't have a credit card so I sent a money order by registered mail. The seller claimed that he didn't receive the payment and requested me to pay by Paypal. I said no and that I would enquire with the post office. The post office was much slower back then. The seller said he couldn't do much so he put the item back online for bidding. The report came in from the post office much later to tell me that the addressee had received the mail and even cashed in the money order.
I don't understand what kind of sick thrill people get from cheating someone else of their money.
And this argumentum ad misericordiam is getting on my nerves.
Talk about a guilty conscience!