
Make your music library and iPhone sing together.
Sync a Large Library to a Smaller iPhone with Smart Playlists 
Even casual music fans can outgrow the 8GB or 16GB of storage on the iPhone. When your total music library is bigger than the phone, take advantage of smart playlists to sync selected songs.
In iTunes, go to File > New Smart Playlist. Un-check the “Match the following rule” checkbox and check the “Limit to” check box. Type in the storage capacity to devote to music in Gigabytes (GB), and select GB from the next drop-down menu. Keep this value small enough to fit alongside your email and apps, too. By default iTunes will select music randomly. However, you can change the way iTunes selects the music by clicking on the last drop-down box and choosing a “selected by” method.
We like to sort by recently added songs, so we don’t miss out on guilty, pop pleasures. Lastly, check the “Live updating” box to make sure your smart playlist is always up-to-date. With the iPhone connected, click its name, and pick the Music tab to manage synced playlists. You can even make a few smaller smart playlists for a favorite band, music genre, or other situation.
Manually Manage iTunes Media 
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If dragging and dropping those one-hit pop wonders to your iPod is your thing, then why not manually manage your media on your iPhone? Manually manage your music and videos to simply drag what you want onto your iPhone, and delete what you don’t want. iTunes will no longer automatically sync media to your iPhone, leaving you in complete control.
To turn on manual management, click on your iPhone in the Devices list in iTunes and select the Summary tab. Once there, select “Manually manage music and videos,” and click the Apply button the bottom right corner of iTunes. To add media to your iPhone, drag music, videos, and podcasts from the Library (or playlist) onto the iPhone in the Devices list, then click the Sync button.
Re-Download Applications from the App Store 
If you accidentally delete a paid download from your Applications folder in iTunes, you don’t need to re-purchase the software from the App Store. All you need to do is revisit the application download page and click Buy App (or Get App if it’s free). iTunes will let you know that you have already purchased the application and that you can re-download it for free. Choose OK, and your application will be downloaded to your Applications folder inside of iTunes.
Replace iPhone Data with a Good iTunes Copy 
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If information stored on your iPhone—mail account settings, contacts, calendars— gets corrupted, you can easily delete and replace the information through iTunes. To do this, plug in your iPhone, and wait until iTunes recognizes it. Click on your phone from the Devices list in iTunes, and then click on the Info tab. Scroll to the bottom, and click Advanced. Browse the options to “Replace information on this iPhone.” (If an item isn’t available, then you haven’t set your iPhone to sync that item.) Select what you’d like to replace, and re-sync your phone.
Stop iTunes from launching when you connect your iPhone 
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Are you annoyed by iTunes launching when you only plugged in your iPhone to charge it? Disable this auto-start in iTunes. In that application, select your device, and click the Summary tab. In the options section, un-check the box labeled “Automatically sync when this iPhone is connected,” and click Apply in the bottom right corner of iTunes.
Check out our other iPhone University subjects:
Fine Photos - Shoot—or at least end up with—snappier pictures with the built in camera
Email Expertise - Manage, send, and receive messages easier than ever
Instant Interface - Learn input secrets for any situation.
Troubleshooting - If your iPhone acts up, here's how to take action.
Safari - Explore the Web broswer like an expert.
Links:
[1] http://www.maclife.com/article/howtos/iphone_tips_itunes
[2] http://www.maclife.com/files/u36/0829_Bohon_Manually_media_700_0.jpg
[3] http://www.maclife.com/files/u36/0829_Bohon_Replace-information_700.jpg
[4] http://www.maclife.com/files/u36/0829_Auto_sync_off_700.jpg
[5] http://www.maclife.com/article/howtos/iphone_tips_photos
[6] http://www.maclife.com/article/[primary-term]/iphone_tips_email
[7] http://www.maclife.com/article/howtos/iphone_tips_interface
[8] http://www.maclife.com/article/howtos/iphone_tips_troubleshooting
[9] http://www.maclife.com/article/howtos/iphone_tips_safari
[10] http://www.maclife.com/article/demystify_your_itunes_album_listings
[11] http://www.maclife.com/article/iphone/app_streams_your_entire_music_collection_your_iphone
[12] http://www.maclife.com/article/hardcore_how_tos_the_digital_media_edition