You can use any kind of bread but I like using the white bread from Asian bakeries the best. The Asian white bread is chewier and more dense than the white bread you see in "Western" markets.
Today I used a little over half of loaf of bread, you get about 5 cups of bread crumb.
First you remove the crusts. It's optional if you don't mind your Panko not being snow white in color.
Tear or cut the crustless slices of bread into chunks. Use the food processor to make the chunks into very coarse bread crumbs. Do not crowd the processor, only fill the bowl about 3/4 of the way full. I had to repeat this step several times since I only have a 4 cup processor.
Spread the bread crumbs on a baking sheet. Bake at 250 degrees F for 15 minutes or until the bread crumbs feel dry. You will want to mix the bread crumbs couple times while baking to insure even drying. Be careful not to brown the bread crumbs.
Remove the baking sheets from the oven. Break the bread crumbs up with your fingers, they tend to stick together a little. Let the bread crumbs cool completely. You can store the bread crumbs in an air tight container or resealable plastic bag for several months in the freezer or 4 weeks in room temperature.