Buy it then find out what it can be used for.
It really depends on the item ...astronomy gear I spend a lot of time thinking about it but say with a car I walk in and say "I will have that one when can you have it ready?"
TV same but I just buy the cheapest.
Phone..I end up with what some fast talking salesman pushes on me just to get out of the place.
But generally I know well in advance the things I want or need..like ride on mower I put it off as long as it was raining and knew I would get a Husky because of an emotional link to the name because Husky was my first and second race bikes...fire pump...only a Honda will do and I bought it as soon as it was clear the old pump was ruined. Houses usually pretty fast buy..if it has what I have asked for...
Thanks for starting such a great thread Hans.
Alex