Entity Retrieval (ER)—in comparison to classical search—aims at finding individual entities instead of relevant documents. Finding a list of entities requires therefore techniques different to classical search engines. In this paper, we present a model to describe entities more formally and how an ER system can be build on top of it. We compare different approaches designed for finding entities in Wikipedia and report on results using standard test collections. An analysis of entity-centric queries reveals different aspects and problems related to ER and shows limitations of current systems performing ER with Wikipedia. It also indicates which approaches are suitable for which kinds of queries.