I do tailors tacking by doing one looped tack and one flat tack through both pieces of fabric. Some people prefer to do a looped tack for every stitch but I feel this is a bit wasteful of my basting thread! Through the paper on my darts etc. I will do looped stitches because cutting them afterwards is also more difficult. I have to do this to all my pieces as I don’t want to chalk onto the fabric as it is not good for the fabric and can always rub off. It is important to mark on my waist line and the hard press line I need to do on the trousers, as well as the turnups.