Your basic function will be
function serverCmdMeme(%cl)
{
//code to be executed when you run the command
}
Announce("message"); will message the entire server, while messageClient(%cl,"","message"); will message the individual client. You can use <color:RRGGBB> to color the text, and <font:fontName:size> to size the font. Also escape codes (ie \c2, \c4) are supported