You've got the exposure spot on.
Generally star trail photography is done by taking multiple 30 sec images over, say, an hour and then stacking them. I use a free programme called Starstax to do this. One of the big advantages of 30 sec exposures is that you can use the continuous drive on the camera to take them and all you have to do is lock down the cable release.
On long exposures there is more chance of hot pixels showing up in the image.
If you want to try to take images with the stars as points of light then you will need to increase the ISO, shoot as wide open (fast lenses are a definite advantage here) and keep your shutter speed to the result of the 500 rule. Just divide 500 by the focal length of the lens that you are using and that is the exposure time. Or alternatively, if you want to shoot longer exposure times, use a tracking mount.
As an example of an hours worth. Please say if you don't want images posted in your thread and I will remove it.
Llawhaden Castle Star Trail