You pretty much have to begin shifting from a stop, going 1st to 2nd. That's what I do, because once you start moving and decide to use it, you have no idea what gear you're in.
If I am moving and want to switch to "sport shift" I'll just give it an up shift so I can see what gear I'm in. An up shift is the safest way I know hoe to do it.
2013 Sterling Gray Mustang GT- ( Bone Stock)
2009 Silver WRX- ( traded for 13' GT)