Understanding Darcs/Reviewing your work
whatsnew
The whatsnew command allows you to get an overview of what unrecorded changes you have made on your working copy.
This way you can get an idea of what needs to be saved.

changes
Changes gives a changelog-style summary of the repo history

diff
Using this command you can get an output like that produced by the diff command. Allowing you to save changes in a plain old (yet very common) format.
Note that darcs does not depend on the diff binary.