You advertise.

Folk music tonight.
Singers Welcome.
Get the local press around to take a picture of you with your guitar and an interview. Put handouts about your new club in local music stores and college notice boards - anywhere musicians might read it. Perhaps the local radio will do an interview or an announcement about the new folk music venue in town.

Choose a nice room - preferably a function room or backroom in a pub. By nice, I mean physically comfortable, a pub not populated by mad looking street characters, clean is good, heated in winter time is good, comfortable seating is good. Ask youself, would I have to be of below average intelligence to want to spend a night in this room.

Best to charge on the door. a small fee - it keeps out people who would talk through other peoples performances and be inattentive. Its best if you can organise it with three or four reliable friends. that means
1) if you are ill the club doesn't close down
2) the whole burden of a residency doesn't fall on you.
3) if one week no other singer turns up - well you just get a longer turn.
4) do a raffle for a bottle of wine or an album in the interval - work towards setting up a fund to attract a professional act occasionally - this way young or inexperienced players get to see the sort of standard they must aim for, a lot of people nowadays simply have never experienced live folk music.

See who turns up!

Its a bit like that Field of Dreams film - set the club up and believe there are folksingers out there who want to share their music.

Best of luck

Some clubs work, some don't. Don't beat youself up if it doesn't. See if there are any lessons to be learned, take a rest then try again.