In regards to what you asked, a good place to start is with 3FC's handy calculators and tools found here :
http://www.3fatchicks.com/diets/diet-calculators.php
The daily needs calculator would tell you (approximately) how many calories your body burns on a daily basis. I've found that these (and FitDay which I use to track my calories, but also gives you a number of calories that it says you burn daily) often overestimate for myself, but you can play with it for a while until you see what it takes to lose. After you figure out your daily calorie needs, you can use simple math to see how fast you want to lose. In order to lose 1 lb a week you would need to cut out (or burn through exercise) 3,500 calories a week, or 500 calories a day, so that's a good place to start. Not knowing your age I guestimated you as having about a 2,000 daily needs calorie number (although you may find that is higher than your body really uses). If you ate 1500 calories a day theoretically you'd lose a lb a week. You don't want to cut out so many calories that it is difficult to stick with, or you will just gain the lbs back. I burn my 500 calorie deficit usually through about 300 calories cut back on food and 200 calories burned through exercise. I find those are ratios I can live with for the rest of my life. Hope that helped, feel free to ask any more questions you have!