Get a ski boot bag for them, put things like ski socks, and other soft packaging round them and put them on as normal luggage - I took mine on the plane just 3 days after I bought them.
Oh, pack things down the leg bits to keep them in shape too.
In your suit case if its big enough. Failing that buy a boot bag, but make sure you wrap your fleeces, thermals etc around your new shiney boots. It protects the buckles from rough baggage handlers.