The VASP Manual
The VASP software is documented on the VASP Wiki.
VASP Workshop Lectures
In 2003 we organized a VASP workshop. The lecture notes and examples from the handson sessions are highly recommended as place to start if you are a beginner and might also be useful if you are not.
Introduction to Computational Materials
Introduction to DFT
Hands-on Session 1, Example Files
Sampling the Brillouin zone
Hands-on Session 2, Example Files
Ionic relaxation methods
Electronic relaxation methods
Hands-on Session 3, Example Files
Accuracy and Validation of results
Pseudopotential Data Base
DFT in depth
Unpaired electrons in DFT
Hands-on Session 4, Example Files
More recently the CSC-IT Center for Science Ltd. in Espoo, Finland, organized two VASP workshops (2006/2009). The lecture notes of those might interest you as well.
You can post requests for technical support on the VASP-forum. Note that technical support is offered as a courtesy only, not as a contractual service.