For the most part you'll probably be able to tell if you are wanted/needed in an event or not. If you're sitting on a bench and all of a sudden a massive earthquake begins and undead rise from the ground all around you… You're in the event. If you come upon another group doing something then quickly, but politely, ask the DM channel if it's ok for you to be there, then, if the DM says yes, RP asking to join the group, just keep in mind that you'll need some reason to want to tag along (studying creatures, hate undead, hope to steal a sandwich...). For the most part just roll with it, for instance, there is no reason to ask if you can stay if the town's walls are under attack, or if there is some other group-oriented thing going on.
