Opening a laptop with one hand in the corner of the screen puts extra stress on the screen. If the laptop is well built then the screen frame takes almost all of this extra stress. The best way to check to see if it is well built is to open it with one hand in the corner of the screen and see if the screen flexes any. If it doesn’t then I wouldn't worry about how you open it; but if it does flex the best way to open it would be at the top middle of the screen using one hand. Also note that using two hands in each corner of the screen can also put stress on it if it is not opened evenly.