1. Select any text and CMD + d to select all instances of the text.
2. With many texts selected use Shift + CMD + Arrows to select all from current cursor position to end or beginning of line, depending on which arrow you use.
(great for cleaning lists of URLs for example)
3. CMD + click to use multiple cursors and edit mutliple places at once
4. CMD + j for joining multiple lines into a single line separated by spaces