iPhone Tip: Use the Spacebar double-tap
The iPhone’s keyboard changes layouts to match the task. When you’re typing a URL into Safari, for instance, the keyboard lacks a space key because spaces aren’t allowed in URLs.
This is usually quite helpful, but it’s not perfect. The default keyboard layout you see in Notes and Contacts lacks a period, which makes it harder to type complete sentences.
Fortunately, Apple designers added a shortcut to work around this limitation: double-tap the space bar to insert a period followed by a space. You can disable this in Settings > General > Keyboard, but it’s quite handy.