It pays to be prepared for that eventuality.
Your first step is to determine which windows are safe to use as an exit. There should be at least one on each level.
The windows you select will need to provide enough space for a person to climb through (at least a 20 inch opening). Make sure everyone knows which windows are “safe exit” windows, and how to open them. Keep in mind that windows may have screens, so ensure everyone knows how to remove those as well.
For a second floor window, consider purchasing a portable escape ladder. These are compact and easily stowed in a closet or under a bed. When you need it, it hangs off the sill and expands into a ladder all the way to the ground. It’s not designed for everyday use, but it will get you and your family out!
Rehearsal is a good idea. You want everyone to know how to get to the nearest “safe exit” window – especially in the dark.
Finally, keep your windows in a good state of repair. According to the National Fire Safety Association, windows should open easily for everyone, and should not have anything in front of them that will prevent or delay a quick exit.