Tips of the day

1. Hidden files in linux start with '.'
Example: .Trash is the usual hidden trash folder name. Similarly .themes for the themes and so on.

2. Many files do not have non-administrative user access. You need to be root user to access those files. It might seem easier to sign in as root but not recommended (In ubuntu signing in as root is prevented by default which can be changed.)
So for root access in commands in terminal, type sudo before the command.
In case you have to access a graphical application, type gksudo
Eg. gksudo gedit /boot/grub/menu.lst to edit the menu.lst file

3. Having used Gnome, KDE and Xfce desktop environments in recent past, I got to learn some facts that might be useful while switching among them.
The file manager (program doing the same function as explorer.exe in Windows) in those desktop environments are:
Gnome - nautilus
KDE - dolphin
Xfce - thunar

The basic text editing softwares (corresponding to notepad in Windows) are:
Gnome - gedit
KDE - Kate
Xfce - mousepad

4. Opening the file manager with gksudo might be a good idea to open/edit or cut-copy-paste restricted-access files the graphical way
eg. gksudo nautilus