Belly fat

Contrary to common misconception, you cannot control where the fat will go in your body. The only way to get the "six pack" look is by reducing the fat in your body, and even then it is not guaranteed. Make sure your body fat drops below 18% (through diet and calorie burning sports), and work on the muscles in your back as well as your stomach.

Note, women are less prone to this look, and will probably have to have even lower fat percentage. 

Obviously I'm no expert on abs, but I know a thing or two about belly fat

As far as I know doctors advise to keep a healthy life style, and try to reduce the inner belly fat. I don't think crunches can help with that.

If you're going for looks rather than health, probably the answer given above will give you all the information you need. 

I would like to just add that if you have a healthy diet, swimming or running on a regulary basis help to tone up your abs. You can combine it with 100 sit-ups or belly crunches but you have to make sure you don´t strain your back. You can do leg raises with your hands on the ground to help you keep your low back down. If the goal is to get a flat belly, doing this should give you visible results in about a month. The most important thing is to be healthy and balance everything.

crunches alone will not remove the fat from around your waist,and some times they can even make you look fatter by devoloping muscles under your fat,the fact is you can't pot reduce fat you can only lose it all over.Try going on a diet and look at some supplements like Acai burn or Green tea best of luck

Again, I don’t think crunched alone will burn fat, they will help to build your abs but to burn fat you need to do caraido and increase your metabolism. Try drinking green tea or taking an extract as it is well known for increasing metabolism and will help to burn stubborn fat 

There are no exact figures on how many crunches should a woman do but too much focus  on crunches is not good and may be counterproductive.

For the exercise do some vigorous exercise such as swimming, sprint, and other exercises of that type. But of course do not overdo it. Doing excessive cardio will actually working against you because you are stimulating excessive cortisol production in your body and breaking down lean muscle tissue... all of which leads to the slowing down your metabolic rate over time and deposition of even more belly fat on top of what you already have.

Wasting most of your workout time with ineffective abs exercises such as crunches, situps, and torso twists actually goes directly against your fat loss efforts as well. You see, the time you waste with doing all of these fairly ineffective abs exercises, is really just keeping you from doing the truly effective full body exercise combinations that actually stimulate your fat burning hormones and increase your metabolic rate for as much as 24-48 hours after each workout. You don't get that with "ab workouts" or "cardio"!

When you get these types of full metabolic exercises right, the excess belly fat starts to melt off quicker than you ever could have imagined. Yes, it IS going to take a little work though. You're not going to be able to just be lazy and sit on the couch every day hoping for your dream body to come true. If you follow these conscientiously, you will be able to remove belly fat once and for all.

The best method to start with is getting a correct diet in oreder. cutting out unwonted sugar and fat or over eating in a single meal can reduce your belly fat fast and doesn't take allot of effort to do.

IT'S ALL IN YOUR DIET

If you do very slow reps and breath correctly you will gain a sick pack very fast.  Theres no point doing 50 if you can do just 20 slow reps, trust me you will feel it more the next day.