To lose weight you need to exercise and eat less. That applies at home and anywhere else, like a gym. You’ve said that you already have the food part down, so I’ll just say that you need to eat a reasonable quantity of healthy foods during the day – portion size is important because the portions you generally see at restaurants are far larger that what an actual portion size is. For instance, an actual portion of chicken breast or steak would be about the size of a deck of cards.
As far as exercise goes, you can try working out with DVDs, which is what I do. You can find a huge variety to try (Kickboxing, Pilates, Aerobics, Weight Training, Circuit Training, Yoga, Dance, etc.) until you find something that clicks for you. I also run on my treadmill on alternate days. You will need cardio to lose weight, but you will also want to incorporate weight bearing exercise, otherwise you will not only lose fat, but muscle too. Also remember that your weight might not go down immediately because muscle weighs more than fat. For that reason, ignore the scale, and pay attention to your clothing sizes and inches instead.
Sit up and ab crunches will only firm your ab MUSCLES. You cannot spot reduce fat, so until you lose weight you might have a six pack, but it will continue to be concealed by a layer of excess body fat. The only way to lose body fat is through cardio/aerobic exercise and you will generally lose it first in the last place you gained it (First hired, last fired). Don’t be in a rush. Weight lost slowly and methodically through sound eating practices and regular exercise is less likely to be regained than weight lost through a crash diet and tortuous boot camp routine. Keep a calendar and write down the workouts you do. I find that keeps me on track. Also incorporate rest days, even though some times you might feel you should work out every day. Don’t do that. Your body needs time to rest and recover or you will stop seeing results (overtraining).
Here are two great sources for workout DVDs:
www.collagevideo.com
www.totalfitnessdvds.com