For the third quarter in a row, fast-food drive-in operator Sonic (NASDAQ:SONC) posted good results. Though same-store sales may be suffering throughout its industry, this drive-in burger chain is doing fairly well.

Sonic reversed a declining trend in revenue growth by boosting sales 31.5% over last year's quarter, and increased earnings per share by 17%. That latter growth came from a net income increase of 12% and the buyback of 5 million shares over the past year, about 5.4% of their diluted share count. Same-store sales growth was 4.5%, atop 5% in the year-ago quarter.

Growth is also coming from new stores; the company opened 43 this quarter, versus 40 a year ago. Sonic is just beginning to penetrate the Northeast (with a new location in Pennsylvania) and the Northwest (with one in my old stomping grounds of Spokane, WA). With much of the northern United States lacking locations, there is still plenty of room for Sonic to grow.

The company is finishing the rollout of the PAYS system, which allows customers to use credit or debit cards right from their cars. At the moment, roughly 72% of all stores have this installed, and Sonic anticipates the rest will have it by the New Year. Letting customers use their credit or debit cards from the comfort of their cars decreases total serving time because it means one less trip to and from the car by servers. Just as importantly, credit and debit card checks average about $2 more per use. Couple that with a usage increase from about 9% to 25% of transactions, and one can see that this will continue to drive growth down the road.

The company also increased advertising to grow brand awareness and encourage more visitors at less usual times, such as breakfast. It plans to spend about 16% more this fiscal year than it did last year. Between its efforts to highlight breakfast, which led to an increase in morning traffic, and the current quarter's jump in overall revenue, Sonic's increased spending certainly seems justified. We'll see how revenue growth for the year goes before considering it money well spent.

Finally, I like management's attempts to solve previous problems. For instance, last summer Sonic was hurt by rising beef prices. To prevent that this year, it negotiated and locked in beef prices through August. Quite Foolish. Of course, depending on the terms of the contract, this Fool can only hope that the spot price of beef doesn't end up falling.

Last October, fellow Fool Jeremy MacNealy pointed out that Sonic was among several beaten-down restaurant stocks. Since then, shares have risen by 14%. From their low in January, Sonic shares rose 27% before falling back to current levels. With Sonic apparently firing on all cylinders and buying back shares, and with decent growth prospects ahead -- management expects18% annual growth in the long run -- the current pullback in price might represent a decent entry point. Just remember to do your due diligence before you fill up on Sonic's shares.

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Fool contributor Jim Mueller does not own shares in any stocks mentioned above. The Motley Fool is investors writing for investors.