First you need to know how many calories you burn in an average day. This can be found on a million different sites. Search for “calorie calculator” and you will find a ton of pages that can give you this information. For the average person this works just fine. For athletes and those with significantly more muscle mass it may give you too low of a number. A good calculator will ask for your daily activity AND for exercise activity. Daily activity is how active you are in your daily life/work. There is a big difference in calories burned for someone who works at a desk compared to one who walks all day (waiter/waitress), to someone who does manual labor. Many mobile apps will calculate this as well.
Once you find your daily caloric needs, take a chunk of calories out to lose weight –SIMPLE!
How much of a deficit do you need?
Many people start with a 500 calorie deficit. So if you need 2500 to maintain, then you eat 2000 calories. If you do this 7 days a week then you have a weekly deficit of 3500 calories which equals 1 pound of fat.
Is this a good place to start? For most people, yes.
You can adjust your caloric deficit accordingly but just know the greater the deficit, the greater the discomfort. Also know that the bigger the caloric deficit, the bigger risk you run of gaining back weight due to the craving from depriving yourself and a decrease in metabolism.
Check out my blog, "Dieting Intensity" to determine how much to eat.