The first couple dates for me generally aren't dining dates unless it's a quick smoothie/coffee/happy-hour date, which gives me an easy out if my date turns out to be insane or some-such. Otherwise I like to do things: hiking, ice skating, local tourist attraction sort of thing. That way I am usually doing something I'd want to do or like doing anyway. If the date turns out well an impulsive bite to eat can follow.
I wouldn't use a coupon early on... that's just isn't exciting. At all. In my opinion it shows that you are more interested in yourself than you are in her or the date.
How would it seem to you if the girl you are out on a first date with busts out a coupon at the end of your dinner? For me, it'd be off-putting and a turn-off. It would signal to me that she didn't suggest the place because she thought it would be a good spot for a date, but she did it so she wouldn't have to pay as much as going somewhere else; thus her priority not being me or the date.
Coupons are for friends and established relationships.