If you are making meals from scratch then yes you need to weigh out your food i.e. if you are making bolognaise then you need to weigh out the correct size portions of mince, spaghetti etc. To be honest it becomes second nature and doesn't take much time up. As time goes on it becomes so much easier as you get an 'eye' for how many points are in a portion.
If you are having pre-packaged food like sausage, southern fried chicken, fish fingers etc etc etc then you just use the nutritional info on the box to work out the points but again you will get to know how many points are in each of your favourite foods of by heart very quickly.
I think to begin with it seems a bit daunting and time consuming, I remember when I first started doing ww I would be rummaging through my cupboards finding out the points for everything but honestly as time goes on it is very easy and simple to work out points.
Hope this helps.