This tip is from reader Mike Arst:
Use the five-way to move the cursor to a spot you want to bookmark. Now press the central button on the five-way twice as if you were double-clicking with a mouse button. This adds a bookmark immediately. It locates the bookmark not just roughly at that location but exactly at that location. It can be confirmed by selecting the bookmark in the “View my notes and marks” menu. When you select the one you created that way, the word that was to the immediate right of the cursor when you double-clicked is the word that appears at the top of the page.