Can someone tell me the "easiest" way to score a cake? What do you use to make the pieces so perfect?

I have a mat that you lay on the cake after the icing has crusted and it makes perfect squares to "score" the cake. I can't remember where I got mine but you can find them several places. hth

I use a metal yard stick most of the time, but I also have a expandable cutter that does a wonderful job, I have seen the mats and am pondering on purchasing one, I am just a hobby baker so no real need yet, so I have found that the yard stick, works ok.