The easiest way to tell if a blade has an edge is to scrape your fingernail wth it. It an edge is there it'll dig in or shave a curl. If it's dull, it'll glide across without leaving a mark. It only takes gentle pressure. You want it to take no pressure to catch.
Depending on how you hold the knife and the kind of pressure applied. You can tear off big chunks, or shave paper thin curls. It all comes with practice.
Kyle