How contemporary? Contemporary homes often have minimal or no trim.

I'm glad you are thinking about this. I have seen many new homes that look weird because emphasis was placed on all the trim except the baseboards. There may be heavy door trim and a foot of molding at the ceiling, and then cheap, 3 inch baseboards. It makes no sense and looks off balance. Personally, I prefer the baseboards to have more weight than the rest of the trim. I would probably look at a lot of pictures or visit open houses and then mimic the trim proportions that look right to me.

Miacometlady, I like the squared off trim as well, and it is so much easier to cut in with wall paint!