As a digital forensics practitioner, we depend so much on tools for our day to day work. Be it commercial or open source. It is good if you could spend some of your time knowing how these tools operate. For a start, look into file carving and specification. You’ll be amazed.
There is a good paper on “The Evolution of File Carving” by Anandabrata Pal and Nasir Memon.
In previous years, DFRWS conducted Forensics Challenge based on file carving. http://www.dfrws.org/