Ken Blanchard (or at least his company) has produced a summary of survey results on leadership and mistakes in leadership.  It is quite predictable that the skill most important and the mistakes most made revolve around communication.

http://www.kenblanchard.com/img/pub/pdf_critical_leadership_skills.pdf

You can use this as tool for an informal evaluation of your leadership.

Thanks to: http://www.thepracticeofleadership.net/2006/09/11/critical-leadership-skills/ for the great link.