I find Open Table easier to use than a phone call to the restaurant, since it is so quick. Log in with your Google Account from your Android device for quickest access. You cannot book two restaurants at the same time, in case you are ever need to do that.
You will also find restaurant reviews, specials and private dining options (for large party planning or special occasions). Menus and photos are sometimes available directly on Open Table, while other times there is a link the individual website. In all, it makes for a reliable open stop shopping for dining.
Recently Open Table has also added the ability to pay for your restaurant tab directly from the app, but I haven't tried that yet. When you are away from your mobile device, their website www.opentable.com is also a great tool.