First, when you see a bridge with skulls fying aroun if you hit one you will lose 50 life and sp, but if you pick up a ghost orb (i know were 2 are)you can run across a bridge and get hit by those ghost things and you will recover 50 life and sp
(note: when you leave the bridge your ghost orb will vanish and you can not change pc on the bridge, the orbs will come back.) Now where to find some. Now, there is one before you go into the first gate, if you walk up to the gate and turn left you should find a path going down the goldish yellowthingy is the ghost orb, walk up to or in it and press a. Another one is where you have to go through the places with the ghost-heads flying around. Before you go in there go up the first flight of stairs and walk behind the log another one should be there.