Even though most ESCs have throttle safety arming built in take caution anyway. I have an ESC in one of my planes that clearly says it will not engage until the throttle is off. I have the Futaba ESC rev syndrome and the first time I powered up to setup servo directions and trims it flew right off my workbench.
edit: Oh and one more thing, provided your ESC safety does work properly it may not arm until both your throttle stick and trim switches are both at their lowest positions.