I reinstall Debian on a regular basis but each time I have to recreate all the users and their directories, is there a way I can do this automatically (excluding the contents of those directories)?

Thank you for your help.

Google for user migration. You may benefit by reading the long version. In short:
Include at least one account of your own for testing.

filter /etc/group for the users and groups that apply.
filter /etc/shadow for the users
filter /etc/passwd for the users
back all of those up.
examine /home (or wherever you home your users) and back up those folders. Optionally, only the folder tree without the files. I recommend backing up the setting files (things like .bash_profile, etc) if those settings matter.
If they matter, back up your mail files for these users. (Generally /var/spool/mail/<username>, depending upon your mail system.

Build your new server

Restore the groups, passwd lines, homes, (optionally the mail), and shadow lines in that order.

Test.

1 members found this post helpful.