This tutorial will help you if you intend to make a realistic night sky.

1. Start with a dark background color. Black, dark blue, whatever.

2. Here's the trick. GO to Effects-->Artistic Effects-->Balls and Bubbles. The settings you will need are as follows: Select the "Automatic multiple Balls or bubbles" option. Coverage: 10 (change this depending on how many stars you want) Average size: 0 Size Variation: 50 Balls or Bubbles type: Intersecting It might not look very "starry" yet, but just wait. Click the "surface" tab. Make the settings as follows: Opacity: 0 Shininess: 100 Gloss: 0 Under the Maps tab, just make sure nothing is checked. Under Illumination: Ambience Maximum: 100 (min doesn't matter) Individual Light properties: Make there be only one light, either by adding or removing some. Mke the color of that light white and set the hightlight size to 10. Finally, click OK. You should get something like this:

If you wish to make a more detailed sky, make several layers of these stars and set the opacity levels differently. You can use this technique to make snow by increasing the highlight size too. Happy starmaking!