If the negative is a loss, totally thin, then you can hold it up emulsion facing you to bright light at an angle so the emulsion is lit, use a black background and see a positive image.

A good thing about computers, you can open a blank document and have a white "light table". Then you can just hold the negative up and look at it that way.

A good negative will have details in the "shadows." You will know if you can see some things in the clear areas.

There's more advice to follow I'm sure, but that can get you started.