It is estimated that 90% of all the analysts in business perform calculations on spreadsheets. Due to advances in technology, spreadsheet applications can now be used on mobile devices and several such applications are available for platforms such as Android and iOS. Research on spreadsheets revolves around several themes, but little work has been done in evaluating the usability of such applications (desktop or mobile). This paper presents lessons learned and usability guidelines derived from laboratory usability testing of mobile spreadsheet applications. Twelve participants were given a task to be solved using a mobile spreadsheet application and based on the video recordings of their interactions with the application patterns of recurring actions and sequences of actions were derived. Navigation, selection, feedback, and transparency of features were some of the main themes in the results of the testing, pointing to a set of guidelines which are also generalizable across other types of mobile applications.