Some people are good at what they do, and some people...well, aren't as good. That's why tutorials are so awesome: because the experts show us amateurs how they do stuff, and we end up with something that looks amazing that we NEVER thought we could do in our wildest dreams! Maybe that's simplifying it a bit, but here's some of the tutorials I've used in the past and have found them to be immensely useful. As I find more I'll be sure to add them!
Decorating Sugar Cookies - http://iambaker.net/sugar-cookie-decorating-101/
Rose Cake - http://iambaker.net/rose-cake-tutorial/