Seriously, it depends on your interests. If you like playing pool, join a pool playing club.
Pool clubs are not exactly famous for being a good place to meet women lol
If you like keeping fit and go to a gym, that's already a club of sorts. Plenty of attractive women go to gyms.
It's almost impossible to start chatting with anyone in a gym, especially without looking like a total creep. It's a really bad idea 99% of the time. People often feel pretty exposed and self conscious in the gym and are generally trying to ignore everyone else, wearing earplugs etc and focus on whatever they are doing. If some sweaty ass dude walks up to you and starts talking to you, that's bound to make things super awkward.
You could increase your knowledge and skills, by doing other courses like a first aid course.
In case someone almost drowns and you give them CPR and they fall in love with you or something?
Otherwise, enroll yourself in a course at a college or university, even as part time. You're bound to meet members of the opposite sex that way, too.
Yes, that's what I said.
Networking and expanding your social circle is the key.
That is... also what I said. But sometimes these things don't work for some people so there is also the other choice.