I created an example form which uses Angular's validation CSS classnames to style tooltips over the form inputs. While entering your password the tooltip helps explain the requirements for the password, for example the password must be at least 8 characters long, and at least one character and one number:
http://jsfiddle.net/adamdbradley/Qdk5M/
This is a port from a jQuery Password strength verification tutorial:
(Disclaimer: Only created for an example of how the CSS classnames can be used, I didn't do any cross-browser/legacy checking)