It would be a million things, but you should start with Cisco's recommend configurations.
On ports that go to other Cisco switches you should use:
interface Gigabit a/b/c
macro apply cisco-switch
On ports that go to Cisco routers you should use:
interface Gigabit a/b/c
macro apply cisco-router
On ports that go to phones you should use:
interface Gigabit a/b/c
macro apply cisco-phone
