For me, it's basic math, and what doctor's say is reasonable.
a) Depending on your personal stats, there is a certain number of calories you can eat to maintian your weight. You can find this number at
http://www.quakeroatmeal.com/qo_livi...nyCalories.cfm. This number is around 2000 for most women.
b) One pound is approx. 3500 cals.
c) For me, the number is about 2100. If I generally cut out 600-800 cals a day [so I eat 1300-1500 cals a day], and I exercise about 3 times a week, burning about 250 cals a workout (30 mins moderate cardio, 10 mins weights). So generally, I cut out around 5600 cals a week, which, divided by 3500, should result in a loss of 1.6lbs a week. Of course, we never know exactly how many cals we are eating, or exactly how much we burn when we work out, but this approximation is a good way to keep tabs on yourself. I admit, I should be having more substaintial workouts, and maybe a few more calories, but we are all finding our way though this. Doctors recommend a 1-2 lb weight loss a week, so this type of cutting cals and upping exercise is a healthy way to weight loss goals.
Again, for me, the long, long off goals are too much for me. I want to lose about 30 lbs, but I have a 6lb. loss goal for September, 1.5 lbs a week, right in the middle of the road. I think one month goals are pretty managable - if you make your goal too far off, you may slack at the beginning and then make unhealthy choices the last month to try to lose the weight. I hope that this post was helpful - a little math can help, but most women who lose naturally aim for 1-2 lbs a week, but you may see a more significant loss at the beginning, due to water weight. So cut cals, up exercise, and water, water, water! Hope this wasn't too preachy, and good luck!