This section of the guide will assume you are using Stellarium, but the instructions apply to other packages as well. First, make sure the software is set to display the sky from the location at which you will be shooting. Enter GPS coordinates if possible, to get the most accurate planning for backroads locations like the dark sky places most of us shoot from. Enter the time and date when you plan to go shoot into your planetarium software. Now you can use the simulation controls (much like a media player control) to slow down, pause, or speed up time in the simulation to see how the sky will change during the shoot. If there is a particular foreground object you want to include in your photos, it is helpful to go during the day and scout the location with a GPS or compass to see where you will need to set up to capture the terrestrial objects with the appropriate star background. For now however, keep in mind the compass heading of the sky objects you're interested in photographing. If you want to photograph Lake Whatever with the Milky Way rising above it, pay attention to where it will be during the shoot, and plan to position yourself accordingly. The exposures you will be doing will be in the 15 second to several minute range, and any lights nearby (and the moon) will invade your images. With a partial moon out of the frame however, you can get neat pictures where you can see stars, the sky is blue, and the landscape looks like daytime however. Pay attention to the moon.
If you don't already know of a dark sky site, free of light pollution, you can use the Dark Sky Finder
(USA) to locate such a place, or try some of the various dark sky maps and services on the web which are useful globally. You'll need a spot away from cities, several miles from high intensity lights used on highways and checkpoints. Preferably with relatively unobstructed horizons, i.e., no trees, power lines, not next to a big hill or building, unless of course you want those in your photos. Pictures of the sky are great, but the best of them have interesting foreground objects which are lit with a strobe, flashlights, or other means to expose them enough to show in the image as well. Mastering this takes practice, so bring several light sources with you to experiment with during your shoot.