I'm also feeding just myself, and like spixiet I buy only the food I need for about a week's worth of meals. I plan my meals in advance (I don't get crazy, I just outline it in my brain). I make sure that what I'm cooking will feed me for at least dinner and a lunch, and hopefully one more dinner. I end making 2 or 3 actual meals a week and make sure to eat the leftovers. A lot of the recipes I use call for the same ingredients, so I'm not having to buy new stuff every time I make a meal. I also have just a couple types of snacks around, like fruit or multigrain pita chips.
Bread is something that I've always struggled to finish before it goes bad, so I put it in the freezer as soon as I buy it and only pull out slices as I need them (a slice of bread thaws in practically a matter of minutes). Milk is another thing that tends to go bad so I've been getting Skim Plus, because it has a longer shelf life. It's a little more expensive but I have time to actually use it all.
And as far as meat goes, I don't buy it unless it's on sale. And if it's not planned into one of my weekly meals, I freeze it and plan on using the week after.
Constantly eating leftovers gets a little boring sometimes, but I'm always looking for new recipes to try so I mix it up from week to week.