Wireless sensor networks consist of a large number of sensor nodes which communicate wirelessly. These nodes are small, battery-powered computing devices equipped with sensors to perceive their environment. Sensor networks are typically deployed in the nature; e.g., to observe the breeding of delicate bird species, to monitor changes of glaciers or to study seismic activities and earthquakes. Several factors contribute to the fact that wireless sensor networks often do not work as expected when deployed in a real-world setting. Some of them are environmental influences which may lead to non-deterministic behavior of radio transmission, malfunction of the sensors, or even the complete failure of a sensor node. In addition to that, scarce resources and missing protection mechanisms on the sensor nodes may lead to program errors. Fixing these problems and errors at the deployment site is difficult, as the inherent characteristics of sensor networks - autonomous, distributed, and resource constrained - hardly allow to get insight into the inner workings of the network. Another common cause for network problems is an unforeseen high traffic load, a so-called \emph{traffic burst}. Such a traffic burst may occur for example, when a sensor network observes a physical phenomenon, and all nodes in the vicinity will try to report at once, causing the occurrence of packet collisions combined with a high packet loss. All these factors contribute to the uncertainty of the sensor network behavior and function. To help with the detection of faults in a deployed network, various active inspection tools have been developed where the sensor nodes are instrumented to actively collect statistical data of their state and communication behavior and forward this data over the radio network to a central station. This additional communication, however, not only increases energy consumption but also changes the nodes' behavior. A further limitation is the fact that no information can be gathered from partitioned parts of the network. With respect to communication, current medium access control protocols use a probabilistic approach to handle concurrent send requests. Although this allows for efficient energy use in the case of infrequent and sporadic traffic, which is typical for wireless sensor networks, probabilistic protocols perform poorly in the presence of synchronous send requests of neighboring nodes. The goal of this thesis is to facilitate the deployment of wireless sensor networks by reducing the uncertainty about the behavior of the network. In order to reduce this uncertainty, we address two distinct areas, namely \emph{fault detection} and \emph{fault prevention}. To detect faults in the sensor node software, we provide tools for the efficient real-time inspection of deployed networks that overcome the problems of the active inspection approach. To prevent faults caused by traffic bursts, we propose medium access protocols that avoid collisions and handle traffic bursts in a deterministic manner. With respect to the outlined problems, the contribution of this thesis is threefold. Firstly, we present a \emph{survey} on problems reported during actual deployments and provide a classification of these. Secondly, to address the problem of the active inspection approach, we propose and evaluate the concept of \emph{passive inspection} of sensor networks. Finally, we propose and evaluate a new \emph{collision-free medium access control protocol} capable of handling bursty traffic. In particular, we show that passive observation of the radio traffic facilitates the development of wireless sensor network applications and improves their deployment. We elaborate on this by supplying appropriate tools which can be adapted for different wireless sensor network applications with low configuration effort. Concretely, we present the \emph{Sensor Network Inspection Framework} (SNIF) which allows to detect faults in a deployed wireless sensor network using passive observation and online analysis. To tackle problems related to traffic bursts, we evaluate different possibilities for collision-free communication in sensor networks and present new techniques for efficient group communication which leverage the broadcast nature of radio communication. By combining existing and new concepts, we realize a collision-free and energy-efficient protocol (\emph{BurstMAC}) that induces only a low overhead compared to current probabilistic state-of-the-art protocols but can handle traffic bursts efficiently.