Selecting

Text in Edit mode.

In Edit Mode, your text has a white cursor, and as in any text editor, it determines where new chars will be inserted.

Select All Ctrl-A

Selects the full text string.

Next/Previous Character Left/ Right

You can move the cursor with the arrow keys.

Next/Previous Word Ctrl-Left/ Ctrl-Right

To move the cursor on a word's boundary.

Line Begin/End Home/ End

Move the cursor to the beginning and end of a line respectively.

Next/Previous Line Up/ Down

To jump between lines.

Next/Previous Block PageUp/ PageDown

To jump back/forward ten lines at a time.

Hold Shift while using the arrow keys to select a part of the text. You can use it to specify different materials, the normal/bold/italic style...