According to the researcher who presented this information, college kids (the population she studied) consider a hookup to be anything from snogging to varioius forms of penetration. Anal does occur, but only in a very small number of cases. Snogging and intercourse accounted for a large majority of hookups and hand and oral sex made up most of the rest. Snogging and intercourse happened equally often; hand and oral sex also happened equally often, but at less than half the rate of the main forms of hooking up.
Most hook ups happened with people who already knew each other. A significant portion (I don’t remember exactly) lead to further hookups, usually with increasingly more types of sexual activity and also with increasing rates of orgasm. If people lasted to six or seven hook-ups, they often had “the talk” in which they decided they were boyfriends and girlfriends, or in an “official” relationship worthy of changing their Facebook status.
In early stages, men had most of the orgasms, but both men and women said they were equally satisfied with the hook-up. The further along they got, more more prevalent female orgasms became and by the seventh hook-up, men and women reported orgasming at about the same rate.
Equal numbers of people ended up in official relationships starting either with hook ups or with standard dating.
It was all pretty interesting. The population studied were college students in large classes like sociology intro classes. They came from some 20 or more campuses in the US. They were surveyed online, and were given extra credit for filling out the survey. The results are not generalizable. But there is reason to believe they are reflective of the college age population in the US.