How to draw a good detail for an item (ex: socket , fixing clips etc.. ) using AutoCAD 2d ?

the best way to do that in AutoCAD2D is to use the block editor to draw all the details you need for an item then you can use it later on at any drawing. You can do your own2D library for all items you common used in your works. Also, the bigger benefit of this block editor that you can make dynamic blocks to define some parameters to you item and then you can use it in any drawing by defining these parameters only instead of doing one by one.