My method: Highlighting the lines I feel are important and must be read. Infact note them down and you'll make your notes out of it.
Some example uses are:
- rotating or scrolling text.
- making portions of a form visible or invisible. For example in an order form, if the user ticks a checkbox "deliver to different address", an extra section with text boxes with delivery streetname, number, and place may be made visible.
- drop down menus.
- retrieving extra information from the server (Ajax) to partially refresh a page.
- validate user input on a form.
- computations without the need to go back to the server.
- determine browser-type.
- obscure some information from certain types of users, such as email addresses from bots.