I got interested in Zentangle about a year ago. I was at an Art store where they had this new art form on display. I went home and cut up some paper into 3x3 squares. At the Art store I bought good Micron Pens. Sold in art and craft stores and Amazon.
Since then I have been doodling. There are several websites with pictures and ideas around. I used You tube to learn myself. There isn't any formula to it...you are encouraged to look around you to detect patterns in your surroundings and start doodling. I found this video really helpful
Here is the link to the official web page where the founder posts and you can search for ideas:
Happy Labor Day