1.Use Stamina Mode
Set the battery mode to stamina mode from Settings App >> Power Management. The Stamina mode switches off mobile data when in sleep mode and switch off Wi-Fi, Bluetooth, Auto sync etc, when they are inactive.This saves the battery that you losses by your carelessness.You may not feel it useful when downloading files since the device cut off the mobile data but it is extremely useful when you are an average user.
2.Share files using NFC
You can share contacts music photos to any one by tapping your phones each other. NFC enables faster transfer of files between two devices.Go to Settings App >> Wireless and Networks >> More to enable NFC file transfer.
3. Set screen time out accordingly
Set Screen time out of you device at minimum level. Go to Settings App >> Display Menu to change the screen time out.All ways remember Xperia z has a bigger screen and require lot of power.
4.Leave phone storage free
It is always better to use a Memory card than using the internal storage of your device.Installed application might require a lot of space and altering the files of phone storage might affect Apps.
5.Use Mobile Back-up Option
Google allows you to back up all the files including Apps, e-books, photos, music etc.Go to Settings >> Backup & Restore and then back your necessary files
5.Tether your device using NFC
Xperia Link allows you to Tether internet to other Xperia smartphone or tablets using NFC.The device scans the QR code of other devices to which the tethering will be activated.