You have to not only be able to speak comfortably in front of groups, but to write proposals and policies and draft documents. You need to be familiar with e-mail etiquette. E-mail is so integral to our jobs and it can be your undoing if you don't use it well. Good HR professionals also need the ability to work with ambiguous direction. This means researching the topic, coming up with ideas, benchmarking other companies, writing a proposal with recommendations - running with it even though you don't have a lot of direction to start with.
Attitude is so important, as is a willingness to take on responsibility and go the extra mile.
We're in a service industry and we need to practice reliability - so that anything you promise gets done. Join professional organizations. Work towards your PHR or SPHR certification. Always look for a solution. Be a problem solver and always offer solutions.