Aligning is the process after you aim the golf club’s leading edge. Most golfers get aim and alignment confused. You must aim the golf club first. Then align yourself to how the golf club is aimed. The same applies to putting.
The difference between putting and all other shots is putting you’re rolling the ball. That said, you have to take into consideration the terrain of each green relative to where your ball is on the green and where the hole is on the green. In other words, to aim your putter and then be able to align yourself correctly you have to read the green correctly in order to know where you intend to aim the putter.
Green reading is entire subject to itself. But the purposes of this discussion, let’s state you’ve read the green and have determined your “aim point”; where you want to start the putt. You simply aim the leading edge of the putter perpendicular to that line. Then you set up yourself, or “align” yourself to the putter.
As you do so, your shoulders are the most important body part to be aligned correctly. The putter is directly connected to your shoulders. Therefore, the putter will most likely move on an arc that is somewhat parallel to your intended start line of your putt. If your shoulders are not parallel to your start line, then you’ll most likely do one of 2 things. Either you’ll make a great putting stroke and totally miss your start line and the hole. Or, you’ll manipulated the stroke and the putter to compensate for your lack of proper alignment, not aim.
To understand how simple a start line adjustment can influence any putt, check out a video I produced about maximizing the break of your putts.