Rapid growth in the usage of location-aware mobile phones has enabled mainstream adoption of Location Sharing Services (LSS). Integration with social networking services has further accelerated this trend. However, sharing location information presents an inherence tension with privacy. Usable access control interfaces are therefore necessary to empower LSS users to manage location disclosures. In this talk, I will present two studies exploring the design of more effective user experience for specifying access control settings. In the first study, participants (N = 103) were asked to specify location access-control rules using free-form natural language. Our findings validated some prior results while challenging others. We also identified several common themes in the free-form rules. In the second study, we used experience sampling (N = 35) to examine various contextual factors that contributed to divergence between privacy settings and in-situ disclosure choices. We found that immediate feedback without an ability to control disclosure outcome evoked feelings of oversharing. Moreover, deviation from specified settings did not always signal privacy violation; it was just as likely that settings prevented information disclosure considered permissible in situ. Our findings further motivate selective control when sharing location with socially distant recipients and when visiting atypical locations. Based on insights from these studies, I will offer interface design enhancements to elevate the usability and effectiveness of LSS access control specification.