I skipped a few spots as I was stitching, and filled them in later. I tried to keep the back as neat as possible, since in a napkin it wouldn't be covered.
Step 4: When you've finished stitching your design, and your needle is on the back of your fabric, run the needle under the back of a few stitches and pull the thread through to secure it. I did that 2 or 3 times, and I'm fairly certain it will hold up well.
Step 5: Remove the embroidery hoop and wash the napkins however you normally wash table linens. I just throw them in with the laundry.
Step 6: Press the napkins, use starch if you want a really crisp look. Fold nicely or dress them up with some pretty napkin rings.
If I was unclear about anything in this tutorial, or you have other questions, feel free to ask in the comments or email me. Let me know if you give it a try. I'd love to see pictures.