It is common for users to explicitly or implicitly compose on-line services to accomplish daily tasks, such as shopping for a pair of shoes on-line. However, unnecessary and repetitive data typing into the services would negatively impact the user experience and decrease the efficiency of service composition. Recent studies have proposed several approaches to help users fill in values to services automatically. However, existing approaches suffer the following two drawbacks: 1) poor accuracy of filling values to services, 2) not designed for service composition. In this position paper, we first present the recent approaches improving the process of filling values to services. We then present our recent achievements and results of using our proposed approaches to help users fill values to services. Lastly, we discuss the various opportunities and challenges in the research field of filling values to services.