Level An Object

Once you place an object how do you level it?
I know you can click on the Gizmo but I always mess up the level. How do I return it to a level position? I don't want to just snap it to the terrain.
I know you can click on the Gizmo but I always mess up the level. How do I return it to a level position? I don't want to just snap it to the terrain.