The biggest thing you need to look out for when you build a page in fireworks is that without rebuilding the html you are stuck to the set size for the content- or you start shifting the layout and creating ugly gaps.
I advise you to create the layout you want, and then look at how it will fit together on a page- if you are not familar with HTML, then use the layout view in DW and convert to tables once you are finished.
Then use the slice tool and export selected slices- if they don't work within the DW layout- reslice and try again.
For menus, I normally crop the menu area, save as, and then export that as html- so the whole table can be dropped into the DW layout, and you are assured that the menu won't get streatched if the tables around it expand.
Sometimes, when my code just won't behave, I take it outside and make it listen to britney spears music, and when it comes back it's really well behaved. I wonder if it's suffering from post tramatic stress syndrome now..