Make a note of the measurements of the existing curtain and lining hems, so that you can make the new hems the same size. These will often be double hems.
Make sure that your hem is not too narrow. A wider hem looks nicer. Curtains made out of light materials have weights sewn into the hem sometimes, which makes them drape nicer. You can sew weights into your new hem as well. Check that it is level using the tape measure, then press. Slip stitch in place. Repeat with the lining hem.
