Harvey, my male cat, is 12, will be 13 in April. He still chases his tail like a kitten - on top of an eight-inch wide ledge, no less. Pretty spry for an old guy.
As for food, the best guidance I can give you is to learn how to read ingredients labels, so you can choose the best of what is available in your area. Here is a website that can help you do that: http://www.catfoodguide.com/long-guide/
It not only teaches you how to read cat food labels, but also gives reviews of some brands. The short version is this. The better foods have specific muscle meats (rather than by-products or meat meals) in the first couple of ingredients. Any grains or other starches are much further down the list - the lower, the better. Avoid by-products altogether. Many cats do not tolerate soy, corn or wheat, so you may wish to avoid those as well. It is unlikely that you will find the better cat foods at Walmart, or at your local grocery store. And yes, you may find yourself standing around in a pet store, reading labels for a long time - I do it myself, whenever I consider a new brand.
If you get concerned that these better brands are costlier, here is something to think about. The cheaper brands are cheaper because they have so much in the way of cheap filler - i.e. grain. Because cats are obligate carnivores, they are not designed to digest grains very well, and do not derive much nutrition from them. In order to get the nutrients that they need from the cheaper foods, cats will eat more. Because the better foods are more nutritionally dense, cats are more satisfied eating less. I know that I can feed my cats portions of foods such as Natural Balance, Eagle Pack, Merrick, Nature's Variety, Wellness, Blue Buffalo, and several others, that are half the size of the portions I fed them of Iams or Hill's products. This offsets the difference in price. Also, I have learned by hard experience that the less I spend on cat food, the more I spend at the veterinarian's office. Of all the times that I have taken my cats to the veterinarian for over the last eleven years that had nothing to do with the quality of the food they eat - there was one birth defect (umbilical hernia), the usual maintenance (shots, spay, neuter, annual exams, dental cleanings), and one infection that were unrelated to what the cats were eating. Every other health issue my cats had, including several episodes of bloody stool, scratching ears bloody from reactions to food allergies, struvite crystals - hundreds of dollars in veterinary costs, were all from diet. So don't forget to factor those costs into your pet food budget, eh? Oh, and one incalculable benefit of feeding the higher quality foods - because they eat less and digest more of it, their poo tends to be smaller and less... um... fragrant.