How to change gamemodes.

How do I change gamemodes?

[editline]25th October 2010[/editline]

Why will no one answer. Christ it used to be so simple to change gamemodes.

Or sv_gamemode <gamemode> before starting a game.

I know how to change gamemodes, I have a GMod server and seriously it’s a build, but… I can change it to Deathrun Fretta Surf etc. :DDDDDDDDDD