Things to avoid in SF:
The Sex Clubs like
http://powerexchange.com/. I've gone with curious girlfriends. It is literally a 150 men to 1 woman ratio. Except it's a sex club. So just like going to the ape house, guys were masturbating to us pretty much the entire time there. Some sex industry people get paid to show up and present floor shows that guys circle jerk around. But your chances of getting laid coming stag are less than zero. Chances of seeing street bum level guys masturbate like they're convicts just released from prison: 100%. If you've ever wanted to have dozens, if not hundreds of men closely circle you and wack off while watching you fuck a woman, then bring a date. She can be the ugliest dog in the world. These guys don't care.
Every Strip Club. They all have an overpriced door fee, 2 drink minimums at $12 each, and the girls are right out of
Candy Diablo's nightmares. Truly a sucky waste of an evening. I buy shots for the table every time one of the girls has knife wound scars. After the third round, they're usually ready to leave.
(Exception: I do like
http://www.lustyladysf.com/ because the girls are fresh and young, it's not a rip-off, has an in-out policy, and is next to some nice cafes on Columbus Street. You can walk in, spend a few bucks to make the window roll down, point to any girl on the floor that attracts you, and her pussy will be kissing the glass within seconds. And then walk out a few minutes later to the cafes. Don't masturbate. Just take that energy into your date later that night. Parking's a bitch in that area though, not worth the effort if you're not already going there.)
SF Halloween in the Castro: Relatively safe and artsy until 4pm, when it starts to become a drunken mob. At sundown the freaky gay shit starts happening in the street and balconies that you'll wish you could unsee for the rest of your life. Ugly scene at every level. Your new art student girlfriend will think it's cool and want to attend. Then once the gay guys take advantage of crowding and start shoving their hands down her pants, fingering her anus and roughly pinching her clit because they're bastards like that, she'll start to cry and sob. Avoid it like the plague.
http://folsomstreetfair.org/ Another gay sausage fest and the few women present are very low class and in weird master/slave relationships, with too many tattoos and piercings. Ultimately a sad, lonely crowd of weird bondage geeks that are fucked up on many, many levels, most of which involve novel ways of avoiding having sex anymore and substituting weird shit for sex.
Any event advertising itself as "Poly" or "Polyandrous". You'll meet fat post-menopausal cougars (with an occasional stunted inbred trailer park denizen) that have spent years carefully constructing this fake little world where they are the only women in it so they can act like alphas. When you invest the time, you'll find they're boring as hell in bed. Sex with them is as meaningless as shaking hands with an old, worn out glove. Or maybe it's like masturbating into a waste can.
China Town New Years parade, Japan Town Cherry Blossom Festival, North Beach Jazz Fest: Maybe once upon a time these were cool, but now they're just crappy street booths, mostly selling long distance phone cards to lower class immigrant families to call their home country. The Mardi Gras parade is fun to be in, but it sucks to be a spectator. You can literally wait an hour for the next crew to arrive, and the crowd is all frat boys with video cameras. Zero women.
Pantsless ride day, Pillow fight day, Zombie day, other flash mobs you'll see on facebook: Too many highschool students.
Chinese News Years Day hunt, Cheap Suit Santa Day, Laughing Squid and
http://sf.cacophony.org/ events: These bitter, angry folks are regularly mean bastards to anyone not in their circle. Which is why they keep recruiting more newbies to be mean to.
http://en.wikipedia.org/wiki/E_Clampus_Vitus events: Fat men who get drunk and smoke while dressing like Morris Dancers. No women.