Sociopaths may not exhibit all of these characteristics, but if 3-5 of the following behaviors are present, you may want to take a "second look" at your acquaintance before allowing him/her into your life.

CHARACTERISTICS OF A SOCIOPATH:

1.    Glibness/superficial charm

2.    Grandiose sense of self-worth

3.    Need for stimulation/proneness to boredom

4.    Pathological lying

5.    Conning/manipulative

6.    Lack of remorse or guilt

7.    Shallow affect

8.    Callous/lack of empathy

9.    Parasitic lifestyle

10.   Poor behavioral controls

11.   Promiscuous sexual behavior

12.   Early behavior problems 
13.   Lack of realistic, long-term plans

14.   Impulsivity

15.   Irresponsibility

16.   Failure to accept responsibility for own actions

17.   Many short-term marital relationships

18.   Juvenile delinquency

19.   Revocation of conditional release

20.   Criminal versatility (Hare, 1986)