Consider quality
Most of us will find the 256Kbps AAC music files created by importing a CD into iTunes are good enough quality.
For the greatest flexibility in future, in case more efficient compression tech arrives, consider switching from the default AAC encoder to Apple Lossless – to do so, click Import Settings in iTunes’ General prefs.
The drawback is Apple Lossless files use more space than AAC, which might quickly use up your Mac’s storage. One fix is to use File > Library > Consolidate Files to put your music on an external drive and manually clean out the originals later on. You’ll find a detailed overview of what this involves at apple.co/2lpHbsL.