This book (real-time rendering) helped me alot! See on page 66 and 70. It has very good graphics and explenation. Quaternions are on page 72 aswell! :)

Rotation about an Arbitrary Axis

This renders the camera with the rotation done by mouse input:

void Camera::getVectors(D3DXVECTOR3& up, D3DXVECTOR3& lookAt)
{
    float yaw, pitch, roll;
    D3DXMATRIX rotationMatrix;
    
    // Setup the vector that points upwards.
    up.x = 0.0f;
    up.y = 1.0f;
    up.z = 0.0f;

    // Setup where the camera is looking by default.
    lookAt.x = 0.0f;
    lookAt.y = 0.0f;
    lookAt.z = 1.0f;

    // Set the yaw (Y axis), pitch (X axis), and roll (Z axis) rotations in radians.
    pitch = m_rotation.x * 0.0174532925f;
    yaw   = m_rotation.y * 0.0174532925f;
    roll  = m_rotation.z * 0.0174532925f;

    // Create the rotation matrix from the yaw, pitch, and roll values.
    D3DXMatrixRotationYawPitchRoll(&rotationMatrix, yaw, pitch, roll);

    // Transform the lookAt and up vector by the rotation matrix so the view is correctly rotated at the origin.
    D3DXVec3TransformCoord(&lookAt, &lookAt, &rotationMatrix);
    D3DXVec3TransformCoord(&up, &up, &rotationMatrix);
}

// The Render function uses the position and rotation of the camera to build and update the view matrix
void Camera::render()
{
    D3DXVECTOR3 up, position, lookAt;

    // Setup the position of the camera in the world.
    position = (D3DXVECTOR3)m_position;

    getVectors(up, lookAt);

    // Translate the rotated camera position to the location of the viewer.
    lookAt = position + lookAt;

    // Finally create the view matrix from the three updated vectors.
    D3DXMatrixLookAtLH(&m_viewMatrix, &position, &lookAt, &up);

    return;
}

With the mouse input you modify head, pitch and roll.

This book (real-time rendering) helped me alot! See on page 66 and 70. It has very good graphics and explenation. Quaternions are on page 72 aswell! :)

Rotation about an Arbitrary Axis

This renders the camera with the rotation done by mouse input:

void Camera::getVectors(D3DXVECTOR3& up, D3DXVECTOR3& lookAt)
{
    float yaw, pitch, roll;
    D3DXMATRIX rotationMatrix;
    
    // Setup the vector that points upwards.
    up.x = 0.0f;
    up.y = 1.0f;
    up.z = 0.0f;

    // Setup where the camera is looking by default.
    lookAt.x = 0.0f;
    lookAt.y = 0.0f;
    lookAt.z = 1.0f;

    // Set the yaw (Y axis), pitch (X axis), and roll (Z axis) rotations in radians.
    pitch = m_rotation.x * 0.0174532925f;
    yaw   = m_rotation.y * 0.0174532925f;
    roll  = m_rotation.z * 0.0174532925f;

    // Create the rotation matrix from the yaw, pitch, and roll values.
    D3DXMatrixRotationYawPitchRoll(&rotationMatrix, yaw, pitch, roll);

    // Transform the lookAt and up vector by the rotation matrix so the view is correctly rotated at the origin.
    D3DXVec3TransformCoord(&lookAt, &lookAt, &rotationMatrix);
    D3DXVec3TransformCoord(&up, &up, &rotationMatrix);
}

// The Render function uses the position and rotation of the camera to build and update the view matrix
void Camera::render()
{
    D3DXVECTOR3 up, position, lookAt;

    // Setup the position of the camera in the world.
    position = (D3DXVECTOR3)m_position;

    getVectors(up, lookAt);

    // Translate the rotated camera position to the location of the viewer.
    lookAt = position + lookAt;

    // Finally create the view matrix from the three updated vectors.
    D3DXMatrixLookAtLH(&m_viewMatrix, &position, &lookAt, &up);

    return;
}

With the mouse input you modify yaw(head), pitch and roll.