Turkey work is an interesting stitch as you begin on top of your fabric and make your first stitch down at A, being sure to hold that tail and not pull it through. Then come up and anchor that tail with a back stitch (B-C). Next, come up at D, right next to A under that back stitch. Go down at E, along your guideline a stitch length away (shorten this length to concentrate more knots per inch), leaving a loop. Stitch an anchor back stitch over that insertion point to secure. And repeat!
When coming up under an anchor stitch (D) it can be easier to split that stitch rather than just slipping under it.
Here's a video:
When filling a shape with Turkey work I like to think of how I would fill a shape with back stitch, which you can see in this video. You can fill with rows, or outline the shape and spiral in towards the center.
Turkey work is a fun way to add LOTS of texture to your hand embroidery work. Keep the loops loopy or trim and shape them.
If your loops are long they may get stitched down by subsequent stitches so I like to leave my turkey work for the end of my project.
Here you can check out the fun ways I used Turkey work in the Polar Pals pattern: