Re: Going for broke ALL the time
If they are a player that essentially stands on the baseline I usually try to hit the ball hard and fast at the drop of their feet. When they try to hit that ball for a winner they ussually dont have a proper swing at the ball and make more errors because of poor technique.
Do this and after a while and they get used to it and start to move to favour their preferred shot. Say they are right handed and their prefered shot is the forehand then they may instinctivly while you are hitting the ball move to their left so they can have a swing at their forhand. At this stage I then aim for their left foot so they are always effectively running out of room. It frustrates the hell out of them.
The key though is to hit it hard and fast so the ball is on them quickly, if you give them to much time they can move into position to hit an easy winner.