Question, i can see on some of the cakes of here that people can get really sharp crisp edges on their cakes with fondant. When I cover cakes in fondant, they tend to get the rounded appearance to them, even if the buttercream underneath was sharp looking before I put the fondant on! Any secret tips/tricks?

I cool it down after adding the buttercreme. the but on the fondant when it is still cold, and you have the sharp edges intackt

Most of the really sharp edged cakes have Ganache underneath the fondant. But to get the best results with buttercream...using a buttercream with at least 1/2 butter....then after you frost the cake put it in the fridge overnight...so the buttercream is really firm! Then take it out in the morning and cover! (also roll your fondant pretty thin!