I always stress out before undertaking dissection. After we are finished the kids learning and curiosity makes it worth the effort. The most useful tools for dissection are a really good dissection kit, quality specimens, and YouTube videos.
One way I saved a little money was on dissection trays. Earthworms are so small I used floral foam from the dollar store. Another great part about dissecting earthworms is they come in a pack of ten which allowed me to demonstrate.
This was a great instructional video that I found to be really helpful.