There are many skills that are critical in this role. Number one is you have to be a good listener. Do more listening than talking. Integrity is very important and credibility is something you have to earn. Adaptability is key, especially in a high-tech environment where you have to be able to change your priorities day to day.
Confidentiality is very important, and being knowledgeable in current HR practices.
I work very hard to stay on top of changes in the field, such as new court decisions. 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.