Rather than having to locate the hang up icon on the screen after each call, you can quickly end a call by pressing the Power button.
To enable this, go to Settings - Accessibility - Power button ends call.
Go to Settings - Display. Then tick the Display battery percentage checkbox. If your phone doesn't have this option, then go to the Google Play store and download a useful App called Battery Percentage.
There are two different Apps under that name, but they are both good.
If you want to remove an entire text message conversation (or thread), go into Messages and look for the thread. Then long press on it and select the Trash icon.
You can also select multiple threads. Before you press the Trash, you can highlight the threads you want deleted. Then press Trash.
To save an image in an email or in the browser, long press on the image and a menu will appear allowing you to save it.
For images inside text messages, you might have to press and hold on the message itself, rather than the image.
To disable / enable vibrate (also called haptic feedback) when you type or press the screen, go to Settings - Language & input - Settings.
Then uncheck Vibrate on keypress.
To add a widget, go to the homescreen and press the Apps icon (the circle with 6 dots). Then you will see a list of your Apps with the word Apps and Widgets at the top. Press Widgets, then you will be presented with a list of available widgets.
To add a widget, press and hold on it and then position it where you want.
To set your voicemail number which allows your phone to automatically input your voicemail password, then open your Dialer App.
Then choose the Phone tab and go to Settings - Voicemail settings - Voicemail number and enter it there.
Depending on your carrier you may have to enter the series of steps required to go through the voicemail menu, for example: *86,,yourpassword# (a comma inserts a pause).
To stop the Photo App or the Music player from indexing your files, place a blank text file called .nomedia in the folder containing your photos or music
Open your music and play a song. Then press Menu - Sound Effects. You will then be presented with an equalizer including presets.
If you are browsing a website and want to see the HTML source code behind the page, then Android doesn't offer you the ability to do this by default.
There is however a handy App called View Web Source which can be installed. Whenever you want to view the HTML of a web page, you just press the Menu - Share - View Web Source.
You can then browse the code or copy the content into the clipboard.