2 questions; how to erase "other memory" on iphone 5 and how to sync to a new computer

Question

Apple support is failing to help my issues so I thought its best to turn to the community. OK so I've talked to Apple before about my "other memory" and I performed a soft reset on my phone and it decreased other memory by maybe a gig. A month later now its higher than it was before at over 5.6 gigs, any way how to make it as little as possible?
Also I just got a new macbook pro and I use to sync my iphone 5 to my macbook (2008), how do I make my macbook pro my primary itunes and still keep all my info on my phone? My new macbook pro itunes says its backed up, but when I plug it in it won't sync any new songs or app data to my itunes, etc.
Any help with these issues will much be appreciated!!

Answer 1

"Other" is all of the data for all of the built in apps. If you delete its contents all of your built in app data will disappear. Some of what is contained in other:
email messages and attachments
Reminders
Calendar entries
Contacts
Text messages
MMS messages and attachments
Genius data
Music cover art
Operating system settings
Safari cache
bookmarks
Game Center status
Music catalog
Probably a few I've missed. There was a problem in an earlier version where deleted MMS messages left behind their attachments, but that has been fixed as of 6.1. Some people suggest deleting your music on the phone. DON'T DO IT! The reason that deleting music recovers some Other space is because it deletes cover art. But is also screws up your music, which will no longer play correctly.
You will find posts from people who said they recovered over 1 GB of space by just deleting old text messages.
If you want Other to be smaller you will have to keep less data on your phone; delete old MMS and texts, delete old email (especially from the "deleted" folder), clear the cache, eliminate cover art.
Your Other is so large, however, that there may be corrupt data contained in it (unless you send a lot of MMS messages with large attachments). If this is the case you should restore the phone as New.
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For your other question, the easiest way is to copy your iTunes library folder from the old computer to the new computer. For the hard way, see: Syncing to a "New" Computer or replacing a "crashed" Hard Drive