If I were to plug my iPhone into my new MacBook Air, would it automatically sync all my music and apps to my new laptop or would it wipe it from my iPhone?
Only music and apps purchased through iTunes can be synced from an iPhone to a computer using Apple supplied software and utilities.
The rest should be synced from your previous computer.
So how do I go about syncing my music from my old laptop?
If you're coming from a PC:http://support.apple.com/kb/PH14328
If you're coming from a Mac:
Retrieving data ...