How can one effectively sharpen circular saw blades by hand?

To effectively sharpen circular saw blades by hand, follow these steps:

1. Secure the blade in a vise to prevent movement.
2. Use a flat file to sharpen each tooth individually at the same angle as the original bevel.
3. File in one direction only, away from the blade's edge.
4. Maintain a consistent angle and pressure while filing.
5. Check the blade periodically to ensure all teeth are sharpened evenly.
6. Remove any burrs with a honing stone.
7. Test the blade on scrap wood before using it on a project.