For the feet: wicking type sock liners and neoprene socks over them - works great!

Rest of the body: good long underwear, fleece sweats or insulated jeans (these are great), then the ol' insulated bibs over this. I go lighter up top for freedom of movent but you can' t beat a good thick fleece/wool sweater. Covering the neck is also important as previously mentioned.

My dad always tends to freeze his nuts off, so he wears his 12-volt heated Harley vest under his coat.