TNBilly is right about balancing the load, if you have a 220 volt gen set, and that is the way I would do it, if I had a 220 volt set. I just have a 1000 watt, 110 volt, set. It won't do more than one thing at a time,so I do just what you are proposing. I turn on a light in the garage window (separate building, wired from the pole not the house), So I know when the power comes back. I turn off the house main breaker. I then turn off all breakers except the one that goes to the outside outlet. I then turn on one breaker at a time as needed to power what I want. It's easier to flip breakers than to move the fridge and freezer to plug them into an extension cord. The furnace doesn't have a cord end it's wired direct.
Also when we have power outages it's usually in the winter and the temps can be below 0 deg. I don't need an open door or window for a cord. I really should buy a gen set with an automatic transfer switch. I'm just to cheap.
Curt