Pay close and careful attention to what is written, looking for inconsistencies. Make frequent reality checks to see that the picture you're building is based on information the other person provided, not what you want them to be. If you have any doubts, don't be afraid to question the other person about them. If they are reluctant to answer or the answers are unsatisfactory, end it. Also ask questions to verify the persons' sex and age group.
Music is another way to date people.
If you think of Paul McCartney as the lead singer of Wings, you belong to a different generation then those who remember him from the Beatles. Remember that you see only a limited number of sides to an individual you meet on-line, so ask about or discuss the everyday things. Taking out the garbage, walking the dog, emptying the litterbox, defrosting the refrigerator or shopping for clothes. So you've met someone on-line, and you're ready to start exchanging pictures or phone calls. A post office box adds a layer of protection between you and them if things turn out badly.