For test tiles and other shapes that I will reuse, I make patterns out of transparent and soft plastic folders (found at the Dollar store). It is particularly good when making series (production work) and you want to save some time. Below is an example for a pair of Christmas Sale seahorse wall pieces. I always start with a sketch (although I could, I choose not to trace directly from a picture).
Then I trace the shape on the plastic folder with a permanent marker, cut the piece out, et voilà! Easy to use, easy to clean and it can be used on both sides.
For test tiles, once I cut a piece in clay I then proceed with stamping a piece of coral and a pencil to make shallow and deeper marks. I also bending the tail so I can get as much information as possible about the glaze’s behaviour. You can see pictures of my test tiles in my previous post on Test tiles.