It depends on which mic you use. Most of the popular large diaphragm condenser mics are "side address." So the cardioid pattern aims toward the singer while the end of the mic points either up or down. The printed brand logo usually indicates which side is the front half.
We like to use a pop screen in front of the mic to protect it. The closer the singer gets to the mic, the more bass it will have. An inch or two works nicely.
Actually, tilting the head back constricts the vocal chords. I tell the singer to singer straight ahead and to ignore where I put the mic. Placement depends on the singer/song/particular microphone used.