A good place to learn basics on webhacking for example is doing the missions @ hackthissite.org.
But do not try to do the missions to impress people. If you get stuck google and read on the subject while you have a good playground to test things, since its legit there. I found that a very nice and playful way in learning some basic techniques.

Oh and you might wanna learn the OSI and TCP/IP - models first ....

Greetz,