There is also a one stroke penalty for hitting the ball into a water hazard. This is another rule that is strictly enforced during professional golf games or sanctioned matches, but not necessarily used for casual games.
Don't try to overpower your shot. A good golfer realizes that the swing is the thing and having good pace and tempo is much more important than muscling up and blasting away. The looser you are when you swing, the better the chance that you will have top clubhead speed at impact. That's what makes the ball go the greatest distance. Knowing NOT to swing as hard as hard as you can represents a greater understanding of the game and allows you to make significant progress.
Practice, practice, practice. Whether you are going to the driving range, the practice green or going to play a round of golf, think about the ramifications of every shot and make the most out of it. You will enjoy your time on the course much more if you try to improve while enjoying your surroundings.