If the tomatoes are dusty, rinse them well and allow them to dry.
Slice tomatoes in half and lay them out to dry, cut side up.
Arrange the slices on a tray for your dehydrator or on a tray you can use outside in the sun (such as a cookie sheet).
If you are sun-drying, cover them with plastic wrap to keep the birds away.
If you are sun-drying, find the warmest spot outside to dry them. (Place them in your dehydrator if you are using a dehydrator.)
Check for doneness every couple of days. The drying time will depend on temperatures and humidity. They are done with they are "leathery."