Notwithstanding that, once a piece is thoroughly learned, I myself and everyone else does, my view is that you shouldn't. You certainly shouldn't need to.
Every muscle in the human body except one* is blessed with a sense that tells the brain where that muscle is in space, or more accurately where it is relation to other muscles. Close your eyes, put your hand above your head, behind your back, out to the left or down to the right and you will know exactly where it is. This sense is known as proprioception. Guitarists in particular and musicians in general use it all the time and if you are serious about your playing, you should do what you can to develop it.
Think a moment about what senses, fundamentally, are used when playing a guitar; touch, proprioception and hearing. Unless you are reading a score or communicating with other musicians sight does not enter into it - so why introduce this unnecessary mental activity into the process? Particularly when, if you are not using it, the most important sense, hearing, immediately becomes more acute.
Don't take your eye off the score to check that your left hand is in position. It causes a mental, and therefore musical, delay. You are in effect training your left hand to not move until your eye gives it permission to - excuse me while I contact my visual cortex and have a moment of uncertainty...wait: second finger, b flat, eighth fret, (de-tuned) sixth string...o.k that's fine, go ahead. Sorry but the moment has passed and the music now has a big ugly dent in it. It would have been better to miss the note but continue playing in time.
As with most rules, there are exceptions. One, paradoxically, is to do with a series of single position changes. Starting in the first position play an ascending chromatic scale of minor thirds on the second and third strings alternating with an open fifth string (such as is found towards the end of the D Major Prelude from the 5th Cello Suite by Bach). Try to do this with your eyes closed and you will soon find that you loose your place. With concentration it can be done but I would never risk it in any practical situation.
Position of the music stand:
No question. Straight in front of you. Not off to the left, not down on the floor, not off to the right. Straight in front of you. If in doubt, sit with a guitar in the classic classical position: left leg up, upper bout below you chin. Relax, look straight ahead - that's where the stand goes.
Dots on the neck of a classical guitar:
Never. There are only eleven frets before the body joins the neck. Eleven equal frets. The fifth and the seventh are no more important than any of the others so why draw attention to them? They are just distractions.
* That muscle is of course the tongue, and that is why, comrades, we feel so compelled to stick it out and bite it whenever we do something vaguely tricky!