Are there any good techniques to get the corners of a square cake sharp and smooth???

I just started using ganache under my fondant...and it works like a dream!!! watch these tutorials...they really helped me!!! The ganache really sets up smooth (check in my photos at the last wedding cake I did...4 tier with flowers) the corners stayed sharp and smooth!

http://www.artandappetite.com/2009/11/ganache-instead-of-buttercream/

http://sugarsweetcakesandtreats.blogspot.com/2010/05/covering-cake-in-ganache.html