I, myself, always avoid standing / walking on graves if at all possible... There have been times I have laid hands on the ground over a grave or on the headstone itself... but always from the side, back, etc...
I can usually tell the boundaries of the actual grave just by sensation, ya know?
BTW... if anyone is "sensitive" - do NOT go within the boundaries of the "Shrine of the Holy Innocents" at Queen of Heaven cemetary... We went there to try and find my father-in-law's plot, and my husband brought me into this portion without telling me WHAT section... I was BOMBARDED by children crying and screaming, oddly enough, I then smelled smoke and all of a sudden felt like I was burning from the inside out... and literally could not stand anymore and fell to my knees in the middle of this graveyard while trying to walk through it... I burst into tears it was so overwhelming...
I *later* found out the reason for what happened...
Anyways, come to find out, 25 of the 92 students from the Our Lady of Angels fire in 1958 are buried there... ALL TOGETHER... it was WAY too much to handle being anywhere NEAR that part...
Little story for ya, I guess...