Here is the list of commonly used commands in Emacs I often use in the daily basis.
Reload a current buffer or working file
Why is this important?
When you are editing a file in an instance of Emacs, it is also opening in the other Emacs window in the circumstance that these instances are on different machine. To work and load the latest content, we should reload the file which is opening in the current buffer before continuing to edit it.
In order to reload a file, you can use the macro M-x revert-buffer (if you want you can bind it to a key), or use a more practice trick: use C-x C-v RET. This tells to find an alternate file and by default, emacs suggests you the current file.
Select a region of text
To select a region, first you set a mark at one end of the text you want to select, and then move the cursor to the other end. To set the mark, you may either press C-SPC or C-@ or enter M-x set-mark-command
C-x SPC, then select your areas by moving the pointer using arrows key. Then use usual commands to delete.