How to open a new tab in the server command line?

What are the keyboard shortcuts to manipulate tabs (open new tab, navigate between tabs ...) in the command line of ubuntu server 12.04?

For doing command line work in general I would recommend using screen, tmux or other of these sort, but to get started, try out byobu:

Default key bindings:

• F2 create a tab
• F3 & F4 you can move around back and forth
• F6 detach session. Resume later - very powerful!
• F7 copy mode - allows you to scroll using arrow keys and search for keywords
• F8 rename window
• F9 Menu & help (more key bindings and features here!)
• type exit, Ctrl+D to exit regularly one shell/window.

Byobu works regardless the type of connection to your server. This works in regular terminals (also desktops), Virtual Terminals, serial TTYs, SSH sessions, etc.

You will need GNU-Screen (sudo apt-get install screen) or you install byobu (a wrapper, that brings GNU-Screen too). From now on you have the possibility to have multiple "windows" in one virtual terminal.
CtrlA c will create another "window"
CtrlA n will switch to the next one
Of course byobu makes it more comfortable :-)