Go to multiplayer LAN and click "Host A Game", then set player limit to 1. After that, uncheck the "Dedicated Renegade" server box (or leave it alone if its already unchecked). Next, set the map rotation and click "Start Game". You will be able to play the maps, without any AI. This is useful for looking around and practicing. Also, you can download mod maps from other web sites and try them out by yourself first. This is functional even if you are offline.