Adding Additional Javascript files

What is the best and most efficient way of adding additional javascript files to the Hemingway Theme?

I am looking to custom build some additional interactivity into my website which uses the Hemingway theme. I naturally took a look at the header.php and saw that all of the stylesheets and javascript files are called by the wp_head function.

Any suggestions on how I can edit the wp_head function to include other files just a javascript files?

Thanks,

Luis Delgado