1). Lids, lids, lids. Go into the kitchen and pull out different sized lids and use them to create nested circles. Lightly trace around the edges and then tangle.
2). Ruler and compass - make concentric circles then use a ruler to draw lines that bisect the circles. Use the intersection points to create a string.
Examples of strings - not tangled yet! The first one has three concentric circles and two lines. The second image has four concentric circles and four ruler lines.
3). Buy mandala stencils from Genevieve Crabe - her stencils give you the intersection points from which to create a pattern. Go to this link to see a video showing how to use them.
4). Use pre-strung zendala tiles from Zentangle.com in either black or white!