Once you start using software like this you find yourself in unanticipated situations, like “this board doesn’t need to be an exact size, so fit it in last around boards that do need to be an exact size.” Sometimes a small adjustment results in a big optimization but you might have to go back in and fudge those for yourself.

Also, one thing you need to account for (and hopefully it’s accounted for by the software) is material loss due to blade kerf. You may also need to account for kerf when it comes time to choose the order of cuts.

http://www.delphiforfun.org/Programs/CutList.htm

I don’t think it’s connected to the one above, it just has a similar name, and I suspect it has many fewer features than the one above, but it worked fine for me when I built some bookcases recently.