There are a few other factors that come into play. First one being whether or not your shotgun barrel is rifled. Shooting skeet with shot is a bit different than rifle/slug.
The concept is obviously similar to shooting a rifle, except that the shotgun slug travels much slower and is heavier, so therefore there is more of an arched trajectory.
The best thing is to get to the range and see how your gun shoots. Check out the ammo manufacturers website, often they will have a generalized trajectory chart.
Good luck and feel free to ask any questions that you may have.