I'd like to know the best strategy for winning a game when I have the lead. No matter how much of a lead you have, it may be difficult to convert the lead into a win. Often you happen to lose the game because of a sudden reversal. To avoid that, I recommend you to calculate the score carefully to work out just how much you are leading by. Often when you think you have the lead, your judgment is unreliable. You might have the feeling that you are leading because because the opponent has made bad shape or has made mistakes, but this judgement is very subjective. When you count the score properly, you may find that the game is actually very close. For example, you may have captured stones that were not really important. To check whether or not you really have the lead and by how much, you have to establish a numerical value for your lead. That will let you know the real status of the game. Good luck!