Standard run-up to get rid of any ice that may have accumulatd during taxi.
On the E170/190;
On a normal takeoff we advance the N1 to 40%, wait for the engines to stabilize and then apply thrust levers to the TOGA detent.
When there's ice/fog we set the N1 to 54% for 30 seconds whilst holding the brakes. If there's noticable fan vibration you let it run longer till it dissapears.
It's good airmanship to notify cabin crew/pax as well of what you're about to do.