Place your couch so that it's "floating" in the room, and not against a wall, or a least the width of your sofa table from the wall.
Position your sofa table behind your couch, either flush against the wall or flush against the back of the couch.
Decorate with small, short ornaments that you can group or gather to make an interesting cluster of color or design. This is a good strategy if your couch is overstuffed and makes people sit back and relax, in which case you might not want very high, tall ornaments placed on the sofa table. People might lean back and knock them over. For this kind of sofa, shells mixed with small vases or glass ornaments look good as do miniature easels with miniature framed artwork.
Decorate a more formal sofa table with objects of various heights. Use different-sized candles and candle holders to bring the focus up and add height to the room. Display plates and artwork, again on easels. You can also vary sizes and shapes of vases and/or glassworks.
Use the sofa table as a coffee table assistant. Keep a set of coaster on it and when space is at a premium, guests can place their drinks on the sofa back table. Likewise, set magazines and books on the sofa table to make room for larger items you want to display on the coffee table.