How to copy with cp to include hidden files and hidden directories and their contents?

Lets say you created the new folder (or are going to create one) and want to copy the files to it after the folder is created

mkdir /home/<new_user>
cp -r /etc/skel/. /home/<new_user>

This will copy all files/folder recursively from /etc/skel in to the already existing folder created on the first line.

Don't specify the files:

cp -r /etc/skel /home/user

(Note that /home/user must not exist already, or else it will create /home/user/skel.)

The correct means of doing this is to use the -T (--no-target-directory) option, and recursively copy the folders (without trailing slashes, asterisks, etc.), i.e.:

cp -rT /etc/skel /home/user

This will copy the contents of /etc/skel to /home/user (including hidden files), creating the folder /home/user if it does not exist; however the -T option prevents the contents of /etc/skel from being copied to a new folder /home/user/skel should the folder /home/user exist.