Take advantage of salad bars in your supermarket. It's a great idea to buy smaller portions of already prepared chopped vegetables you can use in stir-fries and casseroles in addition to salads. In the same vein, look at the bulk section of your supermarket. You can choose exactly the amount you want to buy.
Most canned and jarred ingredients can be covered and stored in the refrigerator if you don't use all of the container. I like to repackage foods that are canned in metal into glass or plastic containers.
Smaller appliances may be a good investment. There are smaller crockpots (called crockettes), toaster ovens, even mini food processors that take up less storage space, use less energy, are easier to clean, and hold just the right amount of food for one or two.
Most recipes can be reduced by cutting the ingredients in half. Be careful when adjusting a baking recipe, because the proportions can be tricky. A recipe scaling program can be a great help. I found one at AllRecipes. When you find a recipe there that you like, a scaling feature is built into every ingredient list. Just type the number of servings you want into the "Scale This Recipe To __ Servings" box below the recipe at AllRecipes and ingredient amounts will automatically be calculated.
Think about combining leftovers into casseroles. There are some great ideas for doing this at Practical Kitchen. And I really like this article on Cooking Solo from North Dakota State University.
Make sure that you are diligent about cleaning out your refrigerator and freezer and discard food that is past its prime. Always remember that it's always cheaper to purchase new food than to have to deal with a food poisoning incident.
Think about starting a cooking club with other singles or couples. This can be a fabulous way to meet people and try new foods - plus you get several days off a week! You can cook larger casseroles and recipes and simply divide them up for each other person in your group. Everyone gets to sample something new, you'll vary your diet and have fun all at the same time.
Cooking a larger quantity of food and using the leftovers in another recipes in the next day or two is also a great way to reduce time in your kitchen. In the recipe for Turkey Tenderloins, for example, you can use the leftover grilled meat in Pasta Turkey Salad the next day, and Cashew Vegetable Turkey Stir-Fry the next. Shopping and cooking for two can be really fun. You can buy what you really like, splurge on more expensive items because the quantity is smaller, and experiment more. Enjoy!