A good place to start: where you work. Work with what you have. You have food all around you. If you work at McD's, have the happy meal (fewer calories, plus the fruit, plus the skim milk = not bad!) and have a salad when you feel like you absolutely have to have something to eat between meals. Vary what you eat but have a calorie budget (McD's lists calories and nutrition info on the box). Find a fresh fruit that you really love and bring some cut up fruit to work in an insulated lunch bag with an ice pack.
Fast food - yum! It has its place. There aren't BAD foods - and good foods, you can eat at home, in moderation. Just keep track of your calories.