You also need to move the target (use camera->setTarget), or the camera will continue to look at the same point in space.
Also, the cross product of the target's direction and the camera's up vector will give you a better sideways direction: http://www.phy.syr.edu/courses/java-suite/crosspro.html
you mean increment both position and target?
camera rotates right and left on up/down arrows and moves back forward on left right arrows.
and what absolute postion mean?
Yes, both the position and target or the camera will appear to rotate.
Absolute position is the position in world space, relative position is the offset from the node's parent.
how do you want to move the camera up? Do you want it to work like the FPS camera and move up when you look up? (which would lead me to ask why you're not using the FPS camera in the first place...)
Anyway, you can move cameras just as usual scene nodes, so check tutorial 4. The only thing which might be astonishing is that you can rotate a camera, but it won't rotate its view. But that was already handled some posts before...