No graphical login at startup

If you find yourself booting up to a non-graphical screen or a console login screen try this tip:

Press simultaneously the keys Ctrl+Alt+F7

Explanation:

There are seven "virtual" terminals running at the same time when you turn on your PC. The graphical desktop runs on the seventh (hence F7) terminal while the other six (F1 to F6) are console (or command-line) terminals.