Learning a good swing plane is essential to playing good consistent golf. A good swing plane is one that allows the club to hit the ball at the same angle the club had at address. To do this, get a full length mirror, colored tape and a friend. Set up so the mirror is facing down the target line and have a friend place tape on the mirror where the club's shaft is. This will give a visual line of where the impact position should be. Using this line, continue making slow motion swings until your body can put the club on that same angle during impact.
Good swing tempo is crucial to a repeatable golf swing. If the back swing and down swing are not on the same tempo, it makes it nearly impossible to hit quality shots consistently. A good tempo to set is having the back swing take twice as long as the down swing to impact. Counting to three is the best way to keep a good tempo. The back swing should be finished once the count is two, and the ball will be impacted on count three.
Always paying attention to the setup position. A good solid setup position can make up for, and even correct, many swing mistakes. The setup starts with getting the body weight evenly distributed over the feet. Then a slight bend at the hips and knees will set a position similar to that of a shortstop in baseball that is ready to move at a moment's notice. Keep your back straight and your chin up, which will give your body plenty of room to make the turn it needs during the swing.