Use bread that is about 3 days old but not completely stale. You can use a box grater or a food processor or to make coarse bread crumbs from bread slices.
Let the crumbs cool off for about 20 minutes, then return them to the food processor and grind them to as fine a consistency as you require. Some people like to grind smaller portions as they need them for specific recipes.
In any case, store your dried bread crumbs in an airtight container and they will last for several weeks.