After one has spent a considerable amount of time practicing drawing the figure without a model (the old saying goes we all have 10 000 bad drawings in us which we have to get out), the next step is to place those figures in a convincing space.
The following images are taken from Andrew Loomis' book "Figure Drawing For All It's Worth" (http://fineart.sk/index.php?cat=1or www.alexhays.com/loomis/). They are an excellent demonstration on how to put the figure into a drawn perspective space.
Leonardo da Vinci using one point perspective:
Examples of other artists placing figures in perspective:
Andrea Del Sarto