For about 3/4 cup crumbs, all you need is two slices of bread.
Yep, that's it. I usually keep bread heels, ends, stale homemade bread, etc. in a ziploc or bread bag in the freezer, then I just pull out what I need.
You want it golden and dry, but not burnt.
Cut into fine crumbs
And, now you have homemade bread crumbs!
Substitution note: usually recipes call for store-bought breadcrumbs, so if you substitute homemade you may need to experiment a little with the amount you use. You may need a different quantity to get the same taste or texture.