When taking photographs at night or in low light situations, you need to first have a since of adventure, be prepared for some educated guessing, previsualize the results you are seeking, and know your equipment, in particular, film and lenses. Since you are dealing with longer time exposures than normal day light photography, you are sharing in the experience of recording the passage of time, which will include cloud formations, stars, and moving objects. You will be faced with a wide verity of types of lighting. You will also need to be aware of the possibility of Reciprocity Failure when dealing with long time exposures. To be successful at low light photography you can follow the three easy steps of shooting a lot of film, taking notes, and reviewing the results, you have recorded on both film and in your notes.
To predetermine and previsualize star trails as past of your composition, locate the North Star in the sky and than compose according to its location. Stars rotate counter-clockwise around the North Star and can be composed to enter, circumference, or exit your composition based on where you place the North Star in your composition. To achieve a star point at night, using 400-speed film and a 2.8 f-stop, the following formula will determine your exposure time. 600 / focal length = max exposure time. If using a 350mm lens, 600 / 350 = 1.7 seconds, not enough time to expose your film. A 50mm lens, 600 / 50 = 12 seconds, a better exposure time. A 28mm lens, 600 / 28 = 21 seconds, an even better exposure time. This means when selecting your lens for your equipment, a lens with a shorter focal length is the better choice when doing low light and night photography. With longer time exposures, you will need to experiment, take notes, and review your results, to create different length star trails and to increase the exposure of light in your composition.
You will need to make careful choices in the film you use. Faster speed films will allow for longer time exposures, but with extreme time exposures may appear grainy in their results. The best film type to use is transparency for better saturation and to avoid color shifts. Exposure in this type of photography is additive, meaning you will need to increase time or aperture size to obtain sufficient light for a properly exposed negative. Light intensity and exposure time are reciprocal. A decrease in one will be balanced by an increase in the other. Some films are less prone to reciprocity failure than others, but it can happen to them all. Reciprocity failure occurs when an imbalanced long time exposure and light intensity cause a shift in color balance, or darkness of an image.
Suggested equipment and supplies include: sturdy tri-pod, short focal length lens or aperture as low as 2.8 (wide angle is best), flashlight, spare batteries for flashlight and camera, and a release cable.
For further detailed reading on this subject, I suggest any of the many books and videos available for check out in our local public libraries.