If you are looking to create terrain to model on, you can turn on your sandbox plugin, draw some quick topo lines (even better if you can get topo lines from an existing map/gis website) and then simply hit the 'from topo lines' tool in the sandbox tool kit and whalla you've got your site topography to model your deck, patio, & landscaping on. Sometimes I prefer to model the landscaping (paths, walls, etc.) in a plan view, then elevate the lines directly over the sandbox topography and use the drape tool to place the lines I need on the generated slope. Lots of tutorials I'm sure on how to use the sandbox tools.