S.B.
I'm naturally thin, but what I always heard was that you take your target weight and multiply it by 10. In other words, if your goal weight is 120, you would consume 1200 calories a day.
However, there are lots of bad calories. You don't want to live on 1200 calories of diet soda per day, for example.
I'm small. I consume more calories each day than I weigh according to the above formula, but I also run my legs off every single day. I am a very active person.
Choosing right calories from proteins, fruits and vegetables and getting plenty of exercise is healthy for anyone, regardless of a "goal" weight.
I know plenty of people who have done Weight Watcher's and it seems to work for them, but I can't wrap my head around the points thing. I know more people who got burnt out on going that route.
What works is different for everyone.
If you are seriously in need of losing weight or changing your eating habits, the best thing to do is make an appointment with a nutritionist who take all of your health into consideration.
Just my opinion.
Best wishes.