I wanted to say too that there are tricks...alot of times you can hide a little wrinkle or a crack or a seam with a stripe or some other planned design you are putting on your cake.
Remember that a camera can hide alot as well...you work on your cake with your eyes 6 inches away from it for hours, so you know every little mistake and lump and air bubble and whatever else...but once its all put together and photographed, alot of that goes away. I have a few photos in my gallery that people have complemented my fondant but I can still see ripples or other imperfections in it!
I would have to say practice makes perfect of course.....but then the untrained eye of the customer and the smaller size of a photograph do wonders to make what we think is an "okay cake" an awesome one!
By the way...if you ever want to feel really good about yourself...pick up a bridal magazine and look at the cakes. Now, in a "cake book" you find alot of absolutely perfect dummy cakes. But in a bridal book...you find real cakes and you can usually find imperfections in them! Bubbles in the buttercream or an uneven fondant stripe or something.
Of course I was at a bridal show in March and it was also a competition...I did my Irish tiered cake...and I ended up trying to get it done in time, so I did not spend as long on my detailing as I should have. Everybody was going past and one girl got real close and inspected it....and said, to a friend, right in front of me real loud, "Wow! You know, they say if you look close even the good cakes have imperfections and this one has a ton! Look at that!" haha.