Doll CakeTwo of the easiest and most useful techniques a beginner can learn are shells and stars.  These are the most common techniques used on kids birthday cakes.  The shells are typically used for borders.  Stars are great for stenciling letters or even characters on a cake.  For the doll cake to the right, the doll bodice and part of the cake are decorated using the star technique.  For the base, I used a ruffle technique but a shell would have been just as nice.  To create the shell, use Tip 21 or 32 and for the star, use Tip 16 or 18.   The Wilton website has detailed instructions and video for the Shell and Star technique.