While some people just aren't good at filling out profiles and prefer to engage on a person-by-person basis, always be wary of the individual who wants a lot of information from you, but is hesitant to share as much of themselves.
Instant Meeting Requests
Relationships that originate online are a safer bet for everyone involved if you get to know each other in text for awhile, then gradually graduate to voice and webcam chatting before meeting in person. Generally a con-artist, player, or other undesirable will let their true colors show sooner rather than later. Text-based communication also allows you to keep records of what was said so you can catch a liar in his or her tracks where they can't weasel out of it.
Dated photos indicate that this is not what this person looks like now. They may have gotten fat, or aged 10 years. While it's natural to put your best foot forward for a good first impression, a dated photo often indicates a certain level of basic dishonesty. Either the individual doesn't plan to really meet anyone or they think you'll get so attached to them you'll forgive them for the dishonesty later.
Phone and Webcam Avoidance
If you've been talking for a few weeks online and the other person refuses to talk on phone or webcam, there could be a problem. Before writing them off though, make sure their reticence isn't because you've asked in a sexual way. Some people are very private and don't want to engage in sexual talk or activity on the phone or webcam. That doesn't make them a liar or con-artist. However, an unwillingness to escalate the relationship contact is an indication of an unwillingness to meet in person.
Asking for Money
It should be common sense not to give a stranger on the Internet money. But when our hormones get involved and we begin to create a fantasy life with someone, it becomes very easy to forget the person we're talking to is really still a stranger. If someone asks you for money for a plane ticket, they may really be financially strapped, or they may just be trying to take your money. If you choose to pay, buy the actual ticket for them in their name. Don't give them money.
Wanting to Come to Your House
An initial in-person meeting should always occur in a safe, public place. Until you meet in person you won't have access to every available body language cue. If this person is a liar, con-artist, cheat, or something far worse, you don't want to be finding out about it when you're alone locked together in your house.