1. A scammer don't usually write details such as number etc about themselves in their profile
2. They usually offer mouthwatery trade e.g selling bitcoin at 400/$ when others are selling at 450 or 500
3. Their mobile number if typed on google brings out information different from what they tell you
4. Their profile is usually new - few months, a year or 2 years old
5. They usually have little or no posts
6. They are always in a hurry during transaction.
7. They use different names and different accounts
8. Block your number immediately after you transfer money to them
9. They sometime come in the name of religion, calling themselves convenat child of God, commited muslim...blah..blah..blah
10. The greedy scammer engages in legit xchange for some period in order to earn your trust and burst you BIG
11. They send money from bank account different from their name. This is MITM technique beware.
12. They write on the thread false scam story so that you would let your guard down when dealing with them
13. They send customise SMS claiming a trusted member vouch for them or false bank SMS alert
14. They sometime claim they don't have nairaland account in order to protect thier moniker.
15. They sometimes claim they can not quote you because antispam bot bans their username. Don't be fooled

How to prevent yourself

1. Trade with trusted xchanger ONLY - This is not 100% guarantee though, but it's more advisable than blind dealing OR
2. Obtain as many vouch as possible before your deal OR
3. Use ESCROW incase you are trading with less trusted fellow
4. Research on identity of the fellow you want to trade with i.e don't rely 100% on my list - confirm my list from your little research

You don't tell us how you make the amount mention in your write up.