If I am making decorations on a cake with fondant, not just covering it, how long does it usually take for fondant to dry? Do I make decorations on the side, let dry and then attach or do I make them, attach and then let dry? Also what is the best way to attach fondant decorations??

It depends on how hard you want your decorations to be. If you want them firm then add a bit a gum tex to your fondant and let them dry for several days. When I did my teapot cake I needed the handle and spout to be somewhat hard....so I let them dry for a few days then I used royal icing to attach them. I also used toothpicks to attach the handle. HTH