Interactive horizontal surfaces provide large semi-public or public displays for colocated collaboration. In many cases, users want to show, discuss, and copy personal information or media, which are typically stored on their mobile phones, on such a surface. This paper presents three novel direct interaction techniques (Select&Place2Share, Select&Touch2Share, and Shield&Share) that allow users to select in private which information they want to share on the surface. All techniques are based on physical contact between mobile phone and surface. Users touch the surface with their phone or place it on the surface to determine the location for information or media to be shared. We compared these three techniques with the most frequently reported approach that immediately shows all media files on the table after placing the phone on a shared surface. The results of our user study show that such privacy-preserving techniques are considered as crucial in this context and highlight in particular the advantages of Select&Place2Share and Select&Touch2Share in terms of user preferences, task load, and task completion time.