One basic tip for using an iPhone 4s is to tap the home screen to see the running apps and then swipe right to bring up the controls where the portrait lock mode will be. Portrait lock stops the screen from switching between landscape and portrait. Another tip involves, double tapping shift to lock in all caps.
To define a word in an app like Safari or Mail, tapping a word twice will bring up the options menu where the word's definition will be. To spotlight search swipe down anywhere on the home screen then type what app is being searched for, anything matching on the phone will appear. To take a quick picture, hold down the volume button to quickly focus the camera.