I can't say that I'm executing the Zentangle in a way that's an accurate reflection of the method designed by Maria and Rick Thomas as I haven't had my class yet (February is just a few weeks away - hooray!). As far as I can tell, however, this one is pretty close to the originators' plan. It was done before I'd really become comfortable with the art form and wasn't venturing too far out of the box just yet.
I start by free-handing a square, then adding a string. From that point I fill up the space using whatever tangle patterns seem appropriate. I try to let the shape of the space or curve of the string dictate the choice of tangle and then allow it to flow from my pen in all its tangled glory. There's a wonderful sense of peace and timelessness while tangling; it seems to suspend all the pending worries and concerns and allow for a window of serenity in a crazy day. The pen nib virtually walks itself across the paper, scribing elegance in its wake while I simply allow it to flow. Ahhhhhh....... *smile*
At this point it can be hard to go on as it's often so pretty in its unshaded state, but onward I bravely plunge! Once again I submit to the flow, allowing the shapes and patterns to dictate their own dimensional appearances as they will, ignoring all learned techniques of directional lighting, turning the tile at will or whim, until - TA DA! It tells me it's done, demands a signature of me and a chance to rest. I sit, sipping tea and resting my eyes on happy artwork, in a perfect and peaceful place.