The easiest way to trace a heart shape is to take one piece of regular printer paper and find something like a bowl or a mug that you can use to trace the top of your heart.
Starting from one edge of the paper, trace the circle 2/3rds of the way around and then either use a ruler or freehand draw a line to the edge of your paper for the bottom of the heart.
Use scissors or a rotary cutter to cut around your template but don’t cut along the straight edge where you started and ended your drawn half a heart.