Most people save money eating out by cutting back on their trips to restaurants. They may leave off the appetizer, avoid alcoholic beverages, but for the most part, they pay full price for whatever they choose to order.
There are other ways though. I talked recently about a coupon book I used to buy in northwest Florida. There are similar books available in most places, and they usually have a good assortment of buy-1-get-1-free offers, which lowers the price of eating out by 50%. Groupon.com is another popular option, which only offers a selected option each day, but if it is something you'd like to try, you can often save well over 50% (in the case of Groupon, not only restaurants but a wide variety of establishments from entertainment, spas, adventures, gourmet desserts, and just about anything else you can think of). Another option is Restaurant.com, which commonly offers $25 dining certificates for $10 (minimum purchase is $35, so in that case you'd be spending $20 on a $35 dinner) ... BUT ... Restaurant.com also offers discounts from time to time as low as $2-4 per certificate, which would allow you to enjoy a $35 dinner for only $12. Restaurant.com certificates should be given to your server before ordering, since sometimes restaurants drop out of the program and you don't want to be hit with an unexpected bill.
I have used all of these methods before, and been very satisfied with them. You can save a lot of money eating out (and sometimes with other businesses as well), and it's a great way to try new places (which is what they offers are designed for).