So I've been learning Blender for the last week or so and have been having a blast!
I did stumble onto a very frustrating problem though. Whenever I duplicate an object using Shift+D, it creates a linked duplicate as if I had used the command Alt+D instead. I first noticed this during a tutorial where the presenter duplicated an object several times and then rotated each one individually. Mine would all rotate together. I thought I might have enabled an option accidentally while following tutorials so I tested this in a brand new scene with just a cube. Sure enough after making a couple of duplicates (Shift+D), any changes made to the original were instantly copied to the duplicates.
I'm not sure if I'm missing something very obvious here, I don't think that is the normal behavior for the Shift+D function. I'm kind of at a loss. Any help would be greatly appreciated!