The edit toolbar
An often overlooked power-tool is the edit toolbar.
Except for the last two buttons on the bar, the way they are used is to select some text (that is, highlight the text), then click on the desired button. This will format the text selected. Here's what the buttons do:
The last two you just click. On the others you can also click the button without selecting text first, which will insert some default text. Just retype over the default text with the text you want to appear there.
The edit toolbar is activated by default. It can be deactivated at the Editing tab in my preferences.
Read more: m:Help:Edit toolbar