When it comes to anything green side, it’s essential to always be very creative. With regards to putting, you should also be extremely creative, even in terms of creating your own drills (probably only if you’re an experienced golfer at around a 15 handicap or better) that you may think are effective. Putting is also mostly a feel related part of the game! However, there are many ways to master the art form.
Alignment is important and it oftentimes helps to buy a putter with an alignment line on the top of the putter head, which should line up right behind the middle of the ball before you make your stroke. I really do highly recommend this for most golfers (especially amateurs), as it’s quite a useful tool!
Another way to optimize your alignment is to stand behind your ball (knowing how to read the green properly) and get a good look at the line of your putt and nearby curvature to also help learn the green’s natural tendencies. Then, pick a spot to putt to, walk into the ball and align your putter face accordingly. As for your feet position, you don’t have to do anything extraordinary. Just stand normally with your feet about (just inside of) shoulder width and the toes of your feet pointing straight ahead and in the same (parallel) line as your putter face.