Hand Signals

[Nevadaref]

Only the games played under NFHS rules use the signals for the different types of fouls. In USSF games the referee just gives the direction.
So from the back of the 2004-05 NFHS soccer rules book the correct signals are:
for obstruction (USSF calls it impeding) touch your fingertips to your breastbone with your elbows out,
for dangerous play extend both arms like a gymnast doing an iron cross with your hands held in fists,
for charging it looks like you put your elbow on your belly/hip and then push it forward (this one looks strange to me).
These signals are pictured on pages 92-93 and are numbered 14, 13, and 9 respectively.