The Japanese word "nampa" originally meant 'moderate party', i.e. a party without opinion or an unassertive person. However, in recent years, "nampa" has been used to refer to people hooked on romance and who chase after the opposite sex, in contrast to the term "kouha", which describes hard-liners who avoid love affairs (preferring other pursuits such as academia). From this, the term "nampa suru" was coined to describe the act of chatting to/trying to pick up members of the opposite sex for fun. "Nampa" usually refers to a guy asking a girl out, while the term "gyakunan" ("gyakunampa", or 'reverse-nampa') is used when a girl approaches a guy. Nampa often takes place out on the street or in a nightclub, and recently "net-nampa" - using dating websites or social networking sites - has also become more common. First of all it's common to go to a cafe, karaoke, or perhaps invite a girl out for a drink, which would all appear to be relatively harmless activities. However, there remains a strong image of "nampa = playing around", plus there have been cases where a girl invited out like this has found themselves the victim of a crime later, meaning there are slightly negative connotations attached to the nampa approach.
