Once you've mastered your targeting and setup position, executing a solid backswing is the next step to a solid golf shot. In the PPGS swing manual, I talk about the importance of the backswing and keeping your elbows in an equilateral triangle position.
Your elbows should be naturally wide. Many golfers tend to drop or tuck their back elbow and drive it into their hip after they start their transition. When you tuck your elbow, you lose that equilateral triangle position, which is so important for making it to a solid impact position consistently. Think "straight up, straight down." It's a vertical motion which allows you to keep the best angles for success.
When you tuck your elbow in the backswing, the club becomes laid off, which makes for a heavy club. Keep it light and keep it vertical!