It's another tip that involves the hand entering the water. This time it is the alignment (position) of the lead hand entering in front of the body.
A common fault among many swimmers is the arm crossing in front of the head (as per the photo below) which can cause the body to become off balance. The legs then end up doing a scissor kick to help stabilise the body but by doing so they end up creating drag as they sink down in the water and kick out to the side. This crossover can also affect the way you start your catch as the lead arm either collapses down under the body or it swings out to the side. For those of you that may get a lower sore back while swimming the twisting of the back/body caused by this crossover may be a contributing factor.
To create good alignment (photo below) in the water the lead hand needs to enter the water and extend forward directly inline with the shoulder. This correct alignment also helps to set you up for a good catch as you are less likely to swing the arm out to the side or for the lead arm to collapse in the water. Some drills to assist in good posture and alignment in the pool are Sidekick, 6/1/6, 6/3/6 and the Javelin drill.