I was a poor college student and I've always been really tight with my money, so I started asking about it at all the restaurants I went to and looking up clubs online -- and I realized tons of restaurants do it. I'm now signed up for about 70 different clubs.
I usually eat free for a week during the month of my birthday, and sometimes even after that because many coupons are good for up to a month later.
A lot of the clubs even send you something just for signing up, so you can get a free meal right away and then another one for your birthday -- some even give you free meals on wedding anniversaries, too. Overall, I probably save close to $500 a year.
My latest free meal was with my boyfriend. We got a $30 gift certificate to a sushi restaurant just for signing up for the club, which was valid until the month after my birthday. So a day before it expired, we both ate all the sushi we could eat and paid a total bill of $5.