Gobzhad... you are quite right on one hand but the points you suggest hitting are not "pressure points" but rather "vital points". [IMG]http://www.fightingarts.com/forums/ubb/smile.gif[/IMG] Vital points striking is intended to cause physical damage to an opponent by blinding, breaking, etc... Pressure point striking is intended to cause particular responses in the opponent by manipulating the sensory nervous system.
As for your orginal question, Jonathan Colley, points can be manipulated in several ways. The three most common categorizations are: hit, rub, touch. This means that some points only need to be touch to activate, some need to be hit and some only cause a response when rubbed. This is because of the different ways the nerves are located in their cavities. Angle and direction is also critical. I can suggest reading a number of books but of course the best way is to find a Sensei to teach them or attend a pressure points seminar.
Happy hunting and best regards to you both.