I prepare my salad fixings on Sunday for the rest of the week. I tear up Romain lettuce and leaf lettuce or add bagged spring mix to the Romaine. I put it in a salad spinner to wash and dry the greens. I then put the greens into a large tupperware container and don't add anything to them. This keeps the greens fresh up to 4 days.
The night before work I make one salad up using some of the greens, add chopped raw broccoli, sliced cucumber, chopped low-fat cheese and chopped up lean ham or turkey and put it into a plastic lunch container. I either cut the tomato into the salad in the morning or just take the tomato to work and cut it into the salad just before I eat. This prevents the greens from getting soggy.
I also keep a bottle of dressing in the fridge at work so I don't have to pack that each day.
I also use my stash of lettuce/mixed greens to throw onto a sandwich or a wrap. It is so much easier to have it prepped for you.
I also pack a snack size container of baby carrots and one of hummous and round out my lunch with some fresh fruit.