Before heading to the gate would be a good time to check the departures board. Since boarding usually starts around T-30 or so, for domestic flights, gate updates for on time departures would have normally been posted by the time you 'headed to the gate".. Not much of a big deal for places like SJC, SFO, or even LAX... but something you need to do for places like DFW or MIA

I would no rely on an SMS text or voicemail for this information, as those methods are not 100 percent failsafe.