Hit to Their Weaker Side
Be sure to pick on their weaker side. Once you hit to their weaker side and take control of the point look for the next opening and put the ball away.
Hit a short angle. If you can hit the ball with a short angle and move your opponent off of the court you may be able to take your next shot and easily punch it into the open court for a winner.
Run Them Around the Court
Start the point by hitting heavy high topspin to one corner then start to really move your opponent back and forth. By hitting so much topspin you may force them back behind the baseline and help to open up the court, just like Agassi does.
Go for the Winner Off of the Return
Play it like Venus or Serena Williams would and just line up the winner and go for it. This is probably the least consistent, but probably the most fun. If your opponent's serve is really so bad that you can consistently go up the line for winners, you will most likely be done with your match quickly.
Put Them in an Uncomfortable Position
If you have a good drop shot and your opponent does not like to play the net, try hitting the drop shot. If they are uncomfortable playing the net then you should have an easier time executing a winner.
If you do not attack a weak second serve and try to put pressure on your opponent you are wasting a great opportunity. Remember, you do not have to hit winners each time to be effective. Move your opponent around the court, hit to their weaker side or any of the other options listed above.
Either way, if you attack the weak second serve your matches will become a lot easier!
If you have a weak second serve, do not fear! Check out my article, Beefing Up Your Second Serve.