The first thing to do is find a picture you like. Or draw it. Whatever the case, if you're a beginner, you will want a picture that is fairly simple (not too much detail). I just printed mine off the internet.
Tape the pic to a cookie sheet and tape (duct tape works best!) either parchment paper or wax paper (doesn't really matter) over it.
Now the fun part: Do the outlines FIRST. Simply take black icing (or whatever color you wish) with a tip 2 and trace over the outlines of the drawing. I mixed black gel coloring with chocolate fudge frosting, it's much easier to get a nice black that way.
FOREGROUND FIRST. For this picture, it was the eyes, basket, and the polka dots on the vest.
I forgot to mention to put your buttercream transfer in the freezer from time to time (in between steps definitely) so it holds its shape.