Tailor’s chalk is still my preferred option for most fabrics as it removes with a light brushing. It now comes in a variety of colours and forms, square, triangular, small rectangles and clutch-type pencils.
There is a special chalk for more delicate fabrics which disappears with steam pressing. There are also no-trace marker pens where the marks disappear soon after being exposed to the air – this means you have to work quickly!
Avoid using pencil unless you know it won’t show and always make sure any marks are within the seam allowance.