Contacting Hiring Manager

What would be appropriate to say when contacting a hiring manager on the unit you are interested in. I have submitted a copy of my resume for human resources but I want to contact the manager as well.. If you have any tips I'd appreciate it. Thanks!
I admire your enthusiasm and persistence - BUT I have a word of warningMany organizations actually do not permit hiring managers to interview anyone until HR 'processes' the application. This is designed to weed out 'problematic' issues and make sure that the manager does not waste time on unsuitable candidates. In large departments, the hiring process is very time consuming and can eat up a lot of a manager's time. This may not be the case for you, but don't be offended or take it personally if you can get hold of the manager.