clumsy columns

Hi all,
Thanks especially to Bob for all your help.

My next question is about multiple columns.

I have a two column page and want to make each column wider, to fit
more text one each page.

I fiddled with the margins and did widen the page a bit, but more then
a little I havent acheived.

The question is besides the page margin and the gap between columns is
there any other parameters that effect column width?

Thanks
Aaron