a hopefully simple question

Okay i have a windows box with an 18GB hard drive, it has a 5gb windows
partition and i wanted to install debian on the rest. Ive never installed
linux on a box that had windows on it, or any other operating system for
that matter. Is there anything i should know before doing this besides
backup? Like a special lilo configuration(or whatever debian uses) or
anythign like that? I have wanted to install debian for a long time but
havent had the chance, now i got the space and the cd's and just need some
advice :)