A D.I.Y layer can manage quite well with six tools
(1) A Roofing Square.
Over the last 50 years I have taught or shown many apprentice vinyl layers how to succesfuly cut in vinyl. This method is fairly safe for fingers, More importantly it is safe for sheet vinyl
(2) The stanly knife

This has proven to be the best shape
(3) Masking Tape
Never write or leave marks on sheet vinyl always write on masking tape

so that any markings can be removed. REMOVE the tape as early as possible.
FELT PEN INK BLEEDS THROUGH