The first step is to call all your mutual friends. If a wanted person in their company there is, maybe, some of them at least vaguely heard where he was going to go missing.
If information about the last movements of wanted your mutual friends and acquaintances there, call the place of study/work of this man. So at least you know were it is at this day in the institution, and if lucky, will tell you with whom together he left the room, and give the coordinates of the last communicate with him.
Think about the habits of your lost friend. Maybe at the same time he always goes to the cafe, gym, massages, etc. If he broke the unit cell, this man is unlikely to change their already established habits. So, if you find it in some of these places, so he's all right - the problem was just in phone.
If the missing person you were supposed to meet, but because of the lack of communication rendezvous did not work, should check their personal page in the social network, log into ICQ, Skype and email. Maybe in one of the programs you are waiting for the letter of explanation: the Internet sometimes are much simpler than a phone. Although hope the news is especially not worth it. Having access to the network, people could send you message or call using one of the newer programs.
Do not be amiss to look into his personal account. Perhaps, thanks to social networking, you will learn the secret side of his life, which will help determine the location of a lost of you relative or friend. If you are seriously puzzled by the loss of a loved person, you can call hospitals and the morgue. About it, of course, do not want to think, but such an option cannot be ruled out.
Take a statement to law enforcement. Most likely, they will act the same as you - to find common friends, asking colleagues, etc. But unlike you, the police have more free hand. They can make a request to the transport service and to obtain information about the movements of the missing personthat you are without authority nobody will.