Cake carving can seem intimidating when you first start cake decorating with one of the biggest challenges being not knowing where to start! My moto is that if you can stack a tiered cake you can pretty much make anything!
It's all a matter of getting your cake tiers to your desired height and then patiently carving and carving and CARVING!!! :-)
It takes a lot of practice - and your first attempts may look distorted - but it gets easier everytime. When I first started out I took photos of every angle of my cakes and then tried to figure out where I went wrong and what I could improve on in subsequent attempts.
Here are some progress photos of the "Santa Claus" cake I made this Christmas. It was a 3 foot tall 300+ serving cake sculpture so it was initially quite a challenge due to the size and weight.
A good practice I learned from it was to screw your dowl to your cake board for added support for heavier cakes. Depending on what your scuplting - if it's heavy on top and lighter on the bottom - it may be prone to toppling over so screwing down the dowl will help with cake wobble as well.
Also using a sturdy cake (stay away from boxed cake mixes as they are very fragile and full of air) will help with the support and structure of your cake.
Here's some photos to give you an idea of the process: