This exploratory mixed methods study describes skills required to be an effective peer reviewer as a member of review panels conducted for federal agencies that fund research, and examines how reviewer experience and the use of technology within such panels impacts reviewer skill development. Two specific review panel formats are considered: in-person face-to-face and virtual video conference. Data were collected through interviews with seven program officers and five expert peer review panelists, and surveys from 51 respondents. Results include the skills reviewers' consider necessary for effective review panel participation, their assessment of the relative importance of these skills, how they are learned, and how review format affects skill development and improvement. Results are discussed relative to the peer review literature and with consideration of the importance of professional skills needed by successful scientists and peer reviewers.