There are a few basic ways you can tell if admin are busy.
@who This will tell you what admin are online and if any GMs have been recently active.
xhelp WITH NO ARGUMENTS. This will also tell you what admin are listening to xhelp currently. It can be less spammy than @who. Just remember that Johnny and Fengshui and some others may not be GMs.
Talk to NPCs You can always talk to an NPC and see if you get a response. Give it a few minutes. If you don't get a response, check back later. You could also ask for an NPC by alias over the SIC.
Anything I missed?