Let's say that you have a library of music that is much larger than the space available on your iPod.
Here is one tactic (there are a variety of techniques that will work)
Click the Browse button in the upper right-corner so the pane-view is enabled.
Select an artist in the pane at the top that you want to exclude from the iPod.
Hold down the
key and click the first checkbox--all the checkboxes for that artist will become unchecked.
Continue for each artist that you want to exclude. You can if you wish, as an alternative, select an album deselect as above
When finished excluding all the artists, click on File>New Smart Playlist
Uncheck the "Match Any of the Following Conditions" checkbox
Check the "Limit To" checkbox and set it to 100 GB, sort by artist
Now click on the iPod Options button in the lower right-hand corner and select this Playlist to sync w/the iPod