Check out these neat stuffed balls. They are made of twelve pentagons, and for the ball to turn out nice and round, these pentagons should be exactly the same. Using a template will produce the same shape each time, but the template should be a perfect pentagon. Perfect, in this case, means more than doing an awesome job, it means that all the sides are the same length, and the angles where sides meet are also the same.
You could use a computer to help you, and print out an image to trace. You could draw one using a compass and ruler, which is very complicated, or you can use this handy trick, it only requires a strip of paper.
Simply tie the strip of paper into a knot (a half hitch, to be precise).
Carefully flatten the knot, keeping the corners touching.
Lastly, trim the strips which are sticking out.
This can be hard to do with a very wide strip of paper, but larger pentagons can be achieved by tracing along a straight edge set against each side of the small paper pentagon.