1. Reduce lag in Touchwiz

Disable S Voice if not frequently used in order Touchwiz look smoother. Another way to speed up Touchwiz is to change a few options in the Developer Options menu. Go to Settings –> More –> About Device. Then scroll down to the build number and tap it seven times. 

2. Extend Your Power

If you have 10% battery remaining and you still need a Samsung Galaxy S4 to work. What do you do? It's easy: to increase the battery life of the Galaxy S4, all you need to do is enable the Power Saving Mode. You can find this option in the Quick Settings panel notification. This feature allows you to activate the power saving, power saving CPU screen or off haptic feedback. For best results, try disabling the third. If that does not work, turn off your data connection.

3. Enable Multiple Window Mode

If you have a lot of tasks, such as emailing while browsing, you just use multiple window mode your Galaxy S4. This feature allows you to run two applications at once, such as email and web browsing for example.
To do this, simply hold down the back button to trigger the multi-window menu, which appears on the left side of the screen. Slide out, choose the application you want to run simultaneously and enjoy!

4. Costumize your notification panel

From the notification pane, tap on the icon that looks like a few squares and two arrows in the very top right corner. Now tap the pencil icon that appears on the left.
From here, all you need to do is drag and drop icons around to move your most-accessed settings into the top five. 

5. Improving the Quality of Your Photos

To enable the highest quality images, you will have to set the size to 13MP by opening the camera and pressing the settings button.

6. Get 50GB Free Cloud Storage for 24 Months

It's very simple: to enable cloud storage for free, simply by downloading Dropbox and then log in. Voila. You have 50GB of free cloud storage for two years. You can enable Dropbox to upload your photos on your cloud storage, which means you will not miss the photos if your phone is lost or stolen. Here Google+ 's photo upload feature works well, and also Dropbox will store your photos in the highest quality.

7. Block Unwanted Calls

To ensure you are not disturbed by unwanted callers, turn on "Blocking Mode" via the My Device.

If you want to reject a certain number, go to Settings -> My device and under "Calls" menu, go to "Auto Reject" enter a specific number, check the box next to it and you'll never hear a call from that person again. You can even tell  GalaxyS4 to send a personal message to the people to explain why their call are rejected.