Use solar glasses or a cardboard solar viewer. It's OK to share them! They should be stamped 'ISO 12312-2'. Make sure they have no scratches, holes or any other kind of damage. They must say 'Solar glasses'. 3D glasses are different and will damage your eyes.  If you wear eyeglasses, put the solar glasses in front of your eyeglasses, not between your eyeglasses and your face. It is important to supervise children wearing solar glasses, to prevent accidental viewing of the Sun without protection.

Test the glasses before the eclipse. If the glasses are too wide or fall off, modify them so the arms stay in place. An idea for modifying them for children is found here: https://www.youtube.com/watch?v=F6qUK1d7U30

Binoculars, telescopes and smart phones may be used but must be fitted with proper solar filters. See the link above for references of filter sources. Using them without filters can permanently damage your eyes and the device and even cause them to burst into flames.

Note: During totality, the Sun's corona can be seen but will be faint to the naked eye, even with magnification. To see it better, wear an eye-patch over one eye in the half hour before totality, to prepare that eye for the dimmer corona. 

#14 welders glasses may also be used as a safe viewing option. 

Other sources of reputable solar glasses and filters: https://eclipse.aas.org/resources/solar-filters.

No eye protection is needed if you face away from the Sun and view the image of the eclipse on a projected surface. Great ideas here: https://www.jpl.nasa.gov/edu/learn/project/how-to-make-a-pinhole-camera/