It is important to be systematic and thorough. You look at your putt from behind the ball. You take time study it,move around, measure in your head and calculate. It is routine any golf player should posses. If, at some point, you introduce other factors like wind, grain, final outcome and so on you may loose yourself in abundance of obstacles. Be reasonable. Acknowledge all factor, follow your instinct and trust yourself. too much doubt is lethal for performance.
If you have a number of thins you want to achieve with one swing and if they are all simultaneously floating while you prepare to hit the ball-no good. Try not to do everything that is in the book. Focus, simplify and go.
Take your mind to nice and quiet place. Do not over analyze and don t exhaust yourself with wish list.
Some people silently repeat their mantra. if that suits you go for it. If you prefer something quite, soothing and no so 'exotic' concentrate on your breathing.
Whatever maintains your balance stick with it.