Get the first two-feet of your swing right and the rest should follow.
The best swings start with a slow, smooth 'one-piece' takeaway.
This means moving your hands, arms, shoulders and hips at the same time in one connected movement as you begin to transfer your weight from your front foot to your back foot.
A good way to visualise this is to 'sweep' the clubhead back rather than attempting to 'pick it up'.
Keep it low to the ground for longer than may feel necessary - this will give you a nice wide arc.
Think of your body as a spring - storing up energy on the way back ready to release it on the way forward.
It doesn't matter how slowly you pull an elastic band back, it's spring is the same. So don't hurry on your backswing.
A good way to check if you have it right is to stop the clubhead once the shaft is parallel to the ground.
Have a look at the clubface.
It should be pointing straight up at 90 degrees to the ground.