This is directly from the Zune
site. Choosing the times you want to sync & sync settings
The sync options in the Zune Music + Video software let you choose how to sync each type of media—music, videos, pictures, and more. Each time you connect your Zune player or Windows Phone to your computer, Zune syncs your media collection to that device immediately according to these settings.
You can choose one of the following sync options for each type of media:All:
Automatically syncs everything of that media type in your collection with your player or phone. When you sync, any media items you added to your collection are also added to your device—as long as there’s enough storage space available. Any items you removed from your collection are also removed from your device.Items I choose:
You choose which specific items or categories of items you want to be synced automatically (for example, you can choose to sync artists, genres, playlists, picture folders, and so forth). Choose an item by dragging it to the Device icon. When you do that, a sync group is created that includes the item. When you sync your device with your collection, any changes you made to items in your collection that are part of a sync group will also be made on your player or phone.Manual:
Choose manual sync to control exactly what gets synced to your device, rather than having Zune Music + Video automatically sync the changes in your collection. When you sync, you manually add and remove items from your device.To demonstrate how these sync options are different, let’s say you just added two albums and deleted one song from your music collection, and you have a Windows Phone. When you connect your phone to your computer:
If your sync setting for music is All, both albums are added to your phone, and the song is removed from it.
If your sync setting for music is Items I choose, nothing is added or removed from your phone unless the music you added or removed is part of a sync group.
For example, say that you have selected an artist as a sync group. The Zune software only adds the albums to your phone if they are by that artist. The software only removes the song from your phone if it is by that artist.
If your sync setting for music is Manual, nothing is added or removed from your phone. You can manually add the albums and delete the song from your phone if you want.To change your sync options
Your sync options are set the first time you connect your device to your computer, but you can change them any time. Settings are specific to each Zune player or Windows Phone you have, so you'll need to adjust the sync options separately for each device.
1. Connect your Zune player or Windows Phone to your computer.
2. In the Zune Music + Video software, click Settings, Device or Phone, Sync Options.
3. Under each media type, select a sync option.
4. Click Ok & you are done.