My advice is first stick to those services you pay for. While it won't weed out all of them, it will significantly reduce the scammers and predators. Question it when things seem to move quickly - even to the point of googling phrases of posts and emails (many professional scammers use form letters of which a lot can be found with a simple search). Research key things (I will use military ranks as an example; ie. a true military man would know that an airforce/army captain is not an equal rank to a navy captain). Take note of the manner in which they write. Do they write in a manner you would expect of their level of education and employment. This is a very big indicator. Poor writing should set off alarm bells. Try to meet the individual as soon as possible and always in a crowded place. If they always give you an excuse - STAY AWAY! And research the name on the internet. DON'T give out your email,personal information, or social media presence if at all possible.