Get in the habit of going to the grocery store and buying what is on sale. I am lucky in this regard because I have a grocery store within a 1 minute walk and I can pretty much pick up my dinner on the day I eat.
For breakfast, I usually eat cereal with Soymilk and I usually throw in a banana, sunflower seeds, dried fruit, or whatever else is lying around my cupboard and looks appealing. Coffee, multivitamin, etc.
For Lunch: Some sort of pasta with plenty of vegetables thrown in or couscous with curry and vegetables including protein from nuts and beans (dry beans from local farmers market--a very cheap way to get quality protein). Multigrain bread or whatever bread is on sale at the farmer's market here in Atlanta. It depends on how my income looks for that week.
Dinner: This varies but I always try to incorporate plenty of vegetables into whatever I'm making.
I have found a vegetarian diet makes me feel better as a runner, but this is not the case for all or most runners.
Also, some of the stuff I listed takes a lot of preparation time (ie soaking beans overnight). However, I'm a grad student and I find time.
I try to avoid eating out unless I am really pressed for time. If you cook for yourself, you will be more conscious about what you eat, I think.