Peter's point about attitude to the customers is a very important one.

There was a thread some while back along similar lines on uk.music.folk and a lot of discussion covered the question of why people dont to clubs as much as they used to. I've snipped some coments I made in that forum from a lengthier post since I felt nobody was addressing the question "why don't they come back again?" so here are some of those snippings in italics below which may fit in here also

Scruffy or not though reasonable comfort for the audience is
essential.

Much has been written in the thread about getting people into the club
bit, unless I've missed it, not much has been written about how to
make sure they come back again.

At the club where I MC, The Old Rose & Crown Walthamstow, I make it a
point to spend some time walking round the room chatting to virtualy
everyone there, it may be just a few words but it's important to make
people feel that they are welcome.

Obviously I don't do this during the actual performances ;-)

I tend to particularly concentrate on new members, asking them where
they found out about the club, if they attend any other clubs or, if
they've been off the scene for some years where they used to go. Is it
the particular guest that night that attracted them or general
interest. Easy simple questions which make people feel welcome and
provide useful info for the club as well. Provide new people who may
not know much about folk clubs and music a general background to the
types of music we feature (which covers a lot....) this may be
particularly important for newcomers who know very little as the type
of music booked on the night in question may not always be to their
taste but soemthing coming up may be. It'll be good of it's kind
anyway :-)

With regulars a general chat about anything. If they've missed a week
or two, polite interest can provide useful info particularly if the
reason they've missed those weeks is to do with who's been booked. You
can find out your audiences preferences quite easily by asking them in
a non threatening way.

Just some of the thoughts I had at that time.