Turn off iPad with home button

In addition to using the physical buttons and screen, if you wish to fully shut-down the iPad, this is most easily achieved from iPad settings:

Settings > General > Shut down

Unless you intend to set-aside your iPad for many days, unused, fully shutting-down the iPad is unnecessary and largely unproductive - as background tasks that execute while the iPad is locked and otherwise idle (such as automatic backup to iCloud, email and message retrieval, alerts and alarms) cannot run.

You should note that, by design, a shut-down iPad will automatically restart when connected to its Power Adapter or other source of external power.