So, put the cursor somewhere and press C-space. The status bar at the bottom of the screen should indicate ``mark set.'' Now using the scrolling and cursor movement commands described in section 3.4 to get to where you want. Everything between your current position and the mark should be highlighted and is now considered the region. The next command will affect the entire region. Two quick shortcuts: M-< and M-> will select from the cursor point to the beginning/end of the buffer, respectively.
If for some reason, the region does not get highlighted as you select it, it means transient-mark-mode has been toggled off. Toggle it back on by entering M-x transient-mark-mode. Apparently, not everyone likes to see the highlighting, though I certainly do.