The GMT programs grdcontour (for data given as 2-dimensional grids) and pscontour (for x,y,z tables) allow for contouring of data sets, while psxy and psxyz can plot lines based on x,y- and x,y,z-tables, respectively. In both cases it may be necessary to attach labels to these lines. Clever or optimal placements of labels is a very difficult topic, and GMT provides several algorithms for this placement as well as complete freedom in specifying the attributes of the labels. Because of the richness of these choices we present this Appendix which summarizes the various options and gives several examples of their use.