Warning signs

The scammer will introduce himself using one of many possible social network sites, dating websites, or email.
Many times an age difference is very obvious. Scams increase with the amount of age between the victim and scammer.
He wants to you send messages only to his private email.
He makes a change to his primary email while you know him.
Country of residence
Look for his profile. If it says something different from where he says he is, than that is a sign to be cautious.
Home country
His profile says he is from the USA, UK or any other country, while in her letter she says she is from Nigeria, Malaysia etc.
Pictures of himself
Keep an eye out for pictures that look like celebrities or very beautiful men. While some may be legitimate, lots of scammers will put up pictures of extremely attractive men as on their profiles. If he sends you a picture, look to see if it is from a magazine or something related.
Spam letters
This scammer will try to get in contact with you via email. You cannot be sure how he received your email address.
Language is off
He may be translating with Google translator, or his English is just very bad. Be careful.
Letters you receive from him
The letters seem strange - maybe they feel generic in quality, or they are not written well. Scammers may even send letters out that are pre-written, and you have already received one from someone else.
He gets your name wrong
You receive messages from him and he calls you something else. Or, your name might appear just once at the top, and that's it.
He doesn't answer any questions you ask of him
He is silent when you ask him something. His personal life and location and address remain a mystery. He will not mention where he works or what his phone number is.
He expresses his love for you within a few exchanges
Be very careful when someone expresses their love for you online after just a few simple correspondences. While you may be worth it, chances are you are either dealing with a child or a scammer. Regardless of how serious he sounds, be very careful before making a commitment, and especially before sending off money.
Money problems
The scammer mentions that he has serious money problems. This could take on an infinite amount of forms. He lost his job, his money was stolen, he needs to pay rent, he got into trouble with the law, he has medical bills, and on and on. He promises that it will be sent back immediately, but it isn't true. Someone he loves had an accident, and needs surgery or medical care. He asks that you pay for it. Be careful, no matter where you are in the world, it is downright rude to ask for money from a person you just met. This is a fake.
He says he wants to see you
All he needs is the right visa, a plane ticket, a clean bill of health from a doctor, insurance, etc... simply put, he needs money to come see you.
He needs money for other misc. things
Scammers will ask for money for a webcam so they can see you, or better yet a new laptop with a webcam attached.
Transfering funds, money orders, and gold/diamond assets
A relative leaves money, but without a secure account he cannot get it. He asks you for your account information to add it.
He needs to ship in gold and diamonds and other such material; however taxes on these items must be paid by you, the victim. He sends out money orders and you need to wire the money over.
He seems to live in multiple places
Most scammers will say they are from the United States or Europe, but working in Africa doing charity work or visiting a friend.