I hear people talking about hooking up, but I’m not sure what that means exactly. If a guy says he hooked up with a girl, what did they do together?
As far as I’ve heard, to hook up means to have sex with. My fellow college students enjoy using this phrase a lot.
When I was an undergrad, it meant either having sex or heavy making out - to the point of having sex without necessarily doing it.
Now, I use it mainly to express having sex - in a one-night stand type of context, not within a relationship.
If a respectable person uses the phrase, they mean to get together for a date. If a dumbshit uses the phrase, then libwen is on the money. I’m going to enroll into highschool so I can make “fuckizzle” a phrase.
Ha, that’s too funny. I’ve heard it used for both. It depends the company you keep - lol! 
My friends and I use it to mean having kissed. Not just a peck, but like open mouth tongue kissing (“French” sounds so silly).
That felt very 7th grade to explain that way.
In my experience, it does not imply anything having to do with the boogie between the sexes. It might well be said that Steve and I hooked up at the Pub and went over to the sports bar where we hooked up with Dan and his pal (all heterosexual guys involved in that exchange).
It really depends on the context. Frex:
“I hooked up with [my friends] last night” = I spent my evening drinking and laughing with my friends, which did not include sex.
“I hooked up with [my partner] last night” = I spent my evening relaxing with my partner, which may or may not have included sex.
“I hooked up with [some guy from a bar] last night” = I spent the latter part of my evening fucking around with a random stranger, which most definitely included sex.
We’uns went fishin’ together.
I’m with Ringo. When I was young, it just meant you met up with someone, male or female, for an afternoon or evening of bullshitting and drinking or shopping or anything BUT fucking. When we fucked, we usually just came out and said we fucked. Or had sex. Or got laid.
In spite of Necro Romancer self righteous objection, “hook up” does, in fact, mean to have some sort of sexual contact with another person. It is debatable whether it only means actual intercourse or includes making out, blowjobs, etc. Personally, I use it as a catch-all phrase and I think for most people that is acceptible.
I should point out that it only applies to one night stands or other casual encounters. You don’t say you “hooked up” with your wife or girlfriend. It is just assumed.
CORRECT USAGE
Jimbo “Hey I hear you hooked up last night!”
Chuck “Yeah she came back with me from the bar”
Jimbo “Do you guys hit it[have sexual intercourse]?”
Chuck “Naw…we just made out for awhile”
Jimbo “Sweet”
INCORRECT USAGE
Scott “Dude!! I hooked up twice last night!”
Brad “Wow!! with who?”
Scott “Sharon [his girlfriend of 2 years]”
Brad “idiot…”
I’ve heard it mean either. Some times it’s implied that there was sex involved, but not always, or else you wouldn’t hear exchanges like this:
" What’d you do this weekend?"
" I went to a frat party… hooked up with a cute guy…"
" Did you have sex with him?"
" No! I wasn’t that drunk. "
I read an article last year in which they talked to middle and high schoolers about the phrase. The younger kids all said it meant kissing, the older ones were split between making out and actual sex.
In college, it meant anything on the sexual spectrum beyond innocuous kissing. Sometimes it mean heavy making out in a dark corner at a party, sometimes it meant sex.