Please help and tell the most commonly used keyboard shortcuts keys for blender.
As said this is too broad and too dependent on what you mean by most commonly used, in your blender usage.
Anyway you can find the shortcut alongside the command in every menu
or in the command search function (Space)
or the full list in the user preference window
where you can even delete, change add them and even create your own custom set (or use one of the predefined ones)
It depends on what are you using Blender for. If you are absolute beginner, I suggest you to watch some YouTube tutorials, I especially like Andrew Price alias BlenderGuru and his beginner series, I am sure you are able to find it yourself.
Then if you want a pure shortcuts overview, I can add a link the official documentation (it is for an older Blender version but they are the same for the current one). https://wiki.blender.org/index.php/Doc:2.4/Reference/Hotkeys/All