It's a good idea to begin each roll with at least one shot made by daylight or flash. This will give the technician in the darkroom a reference frame. Otherwise it is difficult to find the edges of frames against the dark backgrounds of most astronomical images. The results can be disastrous when the film is cut into short lengths for packaging or, in the case of slides, for mounting. To be safe I always ask that my processed film be returned uncut and then do it myself.
Constellations are a good start.
But aiming a camera in the dark has never been easy. Usually only the brightest stars are visible in the viewfinder. But here's a trick I have always found to work. Once your eyes are dark-adapted it's possible to see your hand silhouetted against the sky when looking through the camera. To check where you are aimed, look through the viewfinder and move your hand in front of the lens until it reaches the edge of the field.