(Skip to the point at 0:24 where Stanislas Wawrinka serves out wide)
Anticipation is key. As soon as you see (or know) that your shot will yield a weak or short reply, you must capitalize on it! For instance in this video, Wawrinka knew without a doubt that his cross-court backhand would force a short return, so he quickly approached the net and put the ball away.
Having good judgement and anticipation like this will make your game more efficient; you will always be one step ahead of your opponent!