LG Nexus 5 tips on kitkat

Google Now with Voice Control
Similar to Moto X, Nexus 5 users can now say 'Ok Google' to access Google Now from the home screen using voice control. But first, setup the app by following this: "Google Now > Settings > Language & input > Voice search > Language > English (US).'
Add Widget Simplified Again
No need to open the app drawer to put widgets on the home screen but instead long press on the blank space of your home screen then select the widgets you like.
Quick Settings

Same with Android 4.2 and 4.3 Jelly Bean, swipe two fingers down from the top part of the screen to unhide the notifications area and toggle controls.

Lock Screen Widgets
Android 4.4 KitKat features lock screen widgets such as messaging, email, Google+ and more. Go to "Settings > Security > Enable widgets" then swipe left to right and tapped "+" to add widgets.
Wireless Printing
Printing can be made easy via Cloud Print service on the Nexus 5. Go to "Settings " Cloud Print > Enable > Search for printers."
Installing Non-Market Apps
You can still install apps not found from the Play Store but compatible with Android OS by following this line: "Settings > Security > Unknown sources." Now select the installer aka APK on your file manage to install the app.
Owner Information on the Screen

In case you're hopeful that your lost device bumps itself to Good Samaritan, put owner information so it may be returned to you. Go to "Settings > Security > Owner info > Type in info > Show owner info on lock screen." Facebook or Twitter handles are good start as owner information.

Backup Data and Settings
For certain moments when you need to factory reset the Nexus 5, enable the 'automatic restore' feature to reinstall apps automatically. Go to "Settings > Backup & restore > Backup my data > Automatic restore."
Immersive Mode
You can now read e-books and watch movie in full screen with Nexus 5 running Android 4.4. Once you open the apps, all other elements will be hidden and you can make them reappear by tapping on the screen.
Battery Drainers
Check the apps eating too much battery on your smartphone. Access the Quick Settings then tap the Battery tile to see full details of apps draining battery life on your device.
E-Book to Audio Book
Let Android 4.4 KitKat tell you the story by making e-books work like audio books. Go to "Settings > Accessibility > Enable Talk Back" then launch "Google Play Books > Settings > Automatically read aloud > High-quality voice" to hear good storytelling.
Music Library with Cloud-Based System
Google Music can store up to 20,000 of your own songs without any fee with accessibility from Web or any Android-powered device. Go to your computer > upload songs to Google Music Manager app and make sure to set streaming audio if you have limited data usability. This helps the storage problem Nexus 5 faces due to lack of microSD card support.
Face Unlocking
For cooler unlocking procedure, use the Face Unlock feature which debut back in Galaxy Nexus smartphone. Go to "Settings > Security > Screen lock > Face unlock."
Wallpapers
You can use live wallpapers on your Nexus 5 but only "Phase Beam" is available on the smartphone. You can download lots from Play Store if you desire including from various other Android phones. In addition, static wallpapers can now be previewed before setting it for your home screen.
Pure Hangouts
Since Hangouts support SMS/MMS integration, it may be unusual for some users expecting pure Hangouts messaging. Go to "Hangouts > Settings > Default SMS app > Select the SMS apps." Doing this will require for you to download a third-party SMS app from the Play Store.
Using Moods in Hangouts
As an added fun for Hangouts SMS/MMS service, you can set your mood to let your relatives and friends know what you feel or set emotions at specific given time. Go to "Hangouts > Settings > Set mood."
Snoozing Hangouts
You can snooze notifications on Hangouts for specific time according to your needs. Go to "Hangouts > Settings > Snooze notifications > Set time."
Archiving Messages
Hangouts app allows archiving of both SMS/MMS and online messages on your device. Simply swipe left or right on the thread to put them in the archive list. Select "Settings inside Hangouts > Archived Hangouts" to view them again.
Gesture inside Hangouts
No need to press much on the back key just to get back on the message list inside Hangouts app, simply swipe left to go back or swipe right to view the recent message or select contacts.
Multiple Hangouts Account
Hangouts app on your Nexus 5 can access multiple Gmail accounts you have added on your Gmail app. Inside the Hangouts app, you can see one Gmail account and when you tap it, another account becomes an option.
Data Usage Monitor
Go to "Settings > Data usage" to determine your overall data consumption and which apps are dragging high data. You can also enable 'restrict background apps' to save data consumption.
Home Screen Folders
Same with Android Jelly Bean, hold then drag an icon to another to create new folder with renaming option as well.
Screenshot and Recording

Press and hold 'Volume down + Power' buttons at the same time to screen capture but Android 4.4 offers screen recording as well. Go to the Play Store then download Screen Record to enable recording of screen activity.

Play Games Portal
In Android 4.4 KitKat, Play Games portal now allows tracking of your score and achievements in compatible games and compared your best attempts with your friends and Google+ contacts