Query auto completion (often called suggest) is like magic for users! Seeing suggestions in the query box as soon as a user starts typing their queries dramatically changes the experience. Integrating query suggestions with a search system, however, is not an easy task. We will discuss different types of suggest systems and the most important criteria that a suggest system must satisfy. We will also look at how suggest impacts different search quality metrics as well as define metrics to evaluate the suggest system itself. Finally we will look at implementing our own suggest system using the classes provided by lucene such as WFSTCompletionLookup.