RD, I'm a big fan of bagged salads. I know they cost a lot initially, but when you consider that full heads of lettuce usually go to waste in my fridge and I end up throwing them out only half eaten, the extra charge is worth it. Plus, you can get a lot of variety with the bagged salads, and it keeps you from having to buy four or five different kinds of lettuce.
You might want to stay away from the salad blends that have the dressing, croutons, cheese and fruit in them. That's a sure way to add calories (and fat) very quickly.
I'm in the same situation you're in re: leaving from school to go to work, so on those days I either have a subway sandwich (on wheat bread
) and some soup, or I'll make a quick wrap at home from ingredients that don't have to be refrigerated and keep it in my bag to eat later. If you have soup, try to steer clear of anything that's cream based. It's okay in moderation, but cream based soups are always full of fat (unless it's low-fat stuff that comes from a can). Soups with barley, lentils, and beans give you a lot of protein, nutrients, and help you stay full for a long time.
If you want quick and somewhat healthy "on the go" foods, think about eating a PowerBar Harvest or my personal favorite, Luna bars, instead of doughnuts. They're high in fiber, the Luna bars have lots of soy protein, and they won't make your blood sugar spike like doughnuts will. Plus, they taste REALLY GOOD! The longer your blood sugar stays at a level range, the longer you can go between meals. I think you can get Luna bars on sale in grocery stores or at Wal-Mart for about 99 cents - but I've seen them on sale for as little as 79 cents each.
You might also consider getting some yogurt (if you like it), some sliced or slivered almonds, and some whole grain cereal. Combined, these things make a fantastically filling breakfast, and you get dairy, protein, and carbohydrates all in one meal. Pour 3 tablespoons of cereal and 1 teaspoon of almonds in your yogurt container and eat from the container at red lights.
Re: your caloric intake - what you should be eating to promote weight loss largely depends on your weight and your level of activity, but on average, you need to have a deficit of 500 calories per day (or 3500 calories in a week) to lose one pound per week. You can either lose that 500 calories from limiting your food intake or through exercise, or through a combination of the two.
Okay, this is long enough.. I'm shutting up now
ETA: I thought of something after reading lovelyivy's post... with respect to walking, you might consider interval training. It sounds complicated, but it basically just means alternating between low, moderate, and high activity over the course of your workout. For example, you can try starting out at a leisurely pace for about 5 minutes, then try alternating between a brisk walk and a slow jog. You'd walk briskly for 3 minutes, and try running for 30 seconds (or a full minute if you can handle it). Alternate between the brisk walk and jog for 20 minutes, and finish up with a 5 minute cooldown.
I've been doing interval training on the elliptical trainer and on the treadmill for almost a month now, and I think that it helped me get over my plateau. I've lost 8 pounds over the last 3 weeks.