The ideal speaker set-up for optimum stereo imaging is to place your speakers equidistant from your listening position, at the same relative height (using stands if appropriate) and slightly angled inwards, or 'toed-in', towards your listening position. Imagine an equilateral triangle, with the top point of the triangle being your listening position, and the flat base representing the plane occupied by the speakers simply angle each speaker in so that it follows the triangle back towards its apex, at your seat. Alternatively, you can use a tape measure (and a friend) to achieve the same result use the measure as a 'sight-line', and have your friend angle in each speaker until you're looking directly at its drive units.
This effort will generate a superior 'soundstage' where the speakers all-but-disappear from the room. Instead, the sound should appear to be hanging in space between your speakers, as if it were being generated by a third, invisible speaker. This is the goal of stereo imaging. A true soundstage has both depth (reaching away beyond your speakers to your wall) and height (up towards your ceiling), giving you the sonic scale to cope with anything from the most intimate of acoustic tracks to a full orchestral work.