The first step to comprehend and fix a software bug is usually to reproduce the corresponding failure. Reproducing a failure requires information about steps to reproduce, i.e. the steps necessary to make a failure occur in the development environment. In case of an application with a user interface, steps to reproduce consist of the interactions between a user and the application that precede the failure. Unfortunately, bug reports typically lack this information. Users are either unaware of its importance to developers, are unable to describe it, or simply do not have time to report it. In this paper, we present a simple but effective and resource efficient approach to monitor interactions between users and their applications selectively at a high level of abstraction, e.g. editing operations and commands. This minimizes the monitoring overhead and enables developers to analyze user interaction traces. We map monitored interactions to a taxonomy of user interactions to help developers comprehend user behavior. Further, we present the Timeline Tool that visualizes monitored interaction traces preceding failures. To evaluate our approach we conducted an experiment with 12 participants and asked them to reproduce bug reports from an open-source project. We found that developers are able to derive steps to reproduce from monitored interaction traces. In particular, inexperienced developers profit from the Timeline Tool, as they are able to reproduce failures that they cannot reproduce without it. The monitoring overhead is rather small (approx. 5% CPU and 2-5% memory) and users feel it does not influence their work in a negative way.