There are sites that can calculate the number of
calories you need, but I think the easiest way to do it is to use
your body weight x 15 = number of calories per day to maintain weight. So ..... 168 x 15 = 2520. This figure is obviously affected by how active you are in your day to day life (not including working out). If you have a very physical job, it could be a few hundred higher, if you have a sedentary job and don't get much other exercise, it could be a couple of hundred lower. As you can see, this figure is soemthing of an estimate, but it's a useful place to start.
Your maintenance level is also affected by how much you've eaten in the past. If you've spent several weeks/months at below your maintenance level, your
body may have adjusted to that and set itself a new, lower maintenance. Only you will know if you've done this.
To lose 1lb requires a deficit of 3500
calories, so if you want to lose 1lb a week, you need a deficit of 3500
calories a week or 500 a day. You can achieve this either by eating 500
calories less than you need for maintenance or by burning 500
calories a day through exercise. Your
body doesn't mind.
So, you see that you shouldn't have to go down as low as 1200 to lose weight.
If you want to lose more than 1lb a week, you could cut down the amount you eat and exercise as well, but don't go to extremes with this. To achieve safe, sustainable
weight loss, you should lose no more than 1% of your total
body weight a week, which in your case would be about 1.7lb. The important thing here is not only to lose the weight, but to lose it safely, and to keep it off.
I hope this helps.