I've had a special offer every Saturday for the last five months and have had a handful of clients take it up.
I choose Saturday as it's my quietest day and I hate going out on a Saturday during the day, so am normally at home anyway. And this way it was easy to see how many new clients it would attract. It really hasn't made a difference, maybe one extra client a month. The offer was ?100 for an hour, it's normally ?130. I've had a few 30 min bookings or booking for the evening when the offer isn't on. But in general Saturdays are still dead.