The performance of voltage controlled oscillators (VCO) is of extreme importance for any telecommunication or data communication system. This practical guide develops a systematic, fully-integrated LC-VCO design for low power and low phase noise, especially useful to meet the demands on mobile devices such as cell phones. The proposed VCO design approaches are experimentally verified with several fully integrated CMOS VCOs. The concise presentation is offered in three parts (VCO design; CMOS devices for VCO design; and fully-integrated CMOS VCor GSM) and supplemented by an appendix summarizing the state of the art.