I have read a bunch of posts by Teddy Bear about making sure to keep adequate fresh air "make up" in a home. I assume you mean, simply open a window at all times.

How do I know how many windows to keep open or if only one window, how much to open it?

I have an 1,100 square foot single story ranch home with basement.

I am under the assumption that one window open about 1/4 would do the trick, but wanted to ask the experts.