One of my favorite ways to do this:

# step 1: generate a backup dump
tklbam-backup --dump=/tmp/mybackup

# step 2: interactively review the dump's file contents & disk usage
cd /tmp/mybackup
apt-get install ncdu
ncdu

# step 3: add includes or excludes, go back to step 1, rinse, repeat
vim /etc/tklbam/overrides

# Everything perfect?
tklbam-backup --upload-raw=/tmp/mybackup

By default, TKLBAM will automatically determine what paths and databases need to be backed up on a given TurnKey system according to the backup profile it gets from the Hub. The default profile tracks changes to the user-servicable, customizable parts of the filesystem (e.g., /etc /root /home /var /usr/local /var /opt /srv) while ignoring changes in areas maintained by the package management system.

You can "override" the default backup profile configuration by specifying overrides, either on the command line, or preferably by editing the /etc/tklbam/overrides configuration file.