First, take a portion of your fabric. I have roughly a 1/2 yd which worked fine for me. Open fabric with WS facing up, take the upper right hand corner and create a triangle, lining up the edges and cutting the square. Next fold the triangle in half to have a smaller triangle with only one raw edge side. Iron it flat for clearer lines if necessary.
What makes bias tape special is that it is cut with the grain diagonal. This makes it easier to stretch in one way or another (for things like cuffs and hems) so when you look at your triangle with only one side of raw edge, you should see diagonal grain.
If you have another sewing tutorial you would love to have, or a bias tape experience, please share below!