I go with an overall "feel" and instinct than a point by point breakdown of scores. I am a bit more forgiving on build legality since as a DM I am not one of those guys who is going to check every single feat to make sure you meet the pre-reqs unless you're obviously abusing the game, and I understand that few games actually function in the "RAW Vacuum." However, do NOT take that as a free pass; I will be checking these to the best of my ability and I will dock points if there's a serious screw up.
This is a fairly subjective category for me, and like elegance, it will be based on both concept and execution. If your character has a great, clever back story but is based around blase cookie-cutter mechanics, you will probably score in the 2-3 range. Good story with neat mechanics will earn a 4, especially if it's something mechanical I couldn't have thought of myself. Something reeeeaaalllly out there and unexpected will get you a 5, but be careful as you may take hits in other categories if it's too wacky.
I set a baseline of 3 for power based on what tier
I expect most characters to fall into. For this contest, tier 4 will be 3 points, just like the last contest. Tier 3 performance will earn you 4 points. A few neat tricks and boosts to combat power will get you the half-point bump. Earning a 5 here will be based on how well you explain what the character can do, and if you have any real cool combos or tricks that impress me in the build.
This one is my favorite category, and most builds make or break themselves here. What I'm looking for is whether A) I'd like to play the character and B) as a DM, would I allow the character. Back story also figures heavily here, because as nice as your mechanics may be, without an explanation they are really bland. I don't need you to justify every class level with story, or to shoehorn silly PrC fluff into your background, but it had better make sense conceptually
as to why your character has the levels they have.
Mechanical things I don't like or wouldn't allow as a DM: Flaws, really obscure sources (this means books most people are unlikely to have access to - use common sense here), excessive dipping (some is ok, like the classic Sorcadin build dipping Spellsword, but if there's more than four slashes ["/"] in your class breakdown I'm going to look at it very closely). I won't give a numerical value because this IS still subjective; some builds can get away with a flaw or something if they really work well otherwise, others....can't.
Obviously a build being blatantly illegal or doing something really questionable that would probably earn a "NO" at most tables will make your score drop here, but as I mentioned at the start I will still be forgiving if I can see that you were trying to build around a good concept (probably earning a 1.5 or a 2).
Use of Secret Ingredient:
How well you do here depends heavily on how you did on the other 3 categories, and whether the PrC in question was key to that success. If your build couldn't have hit the power and elegance levels it did without using the secret ingredient, expect to do well. If you got a low originality score and plain 2 or 3 in the other two, you will still score low here even if you had all 10 levels of the PrC. My main rule here is yes, please use the PrC a lot, but use it well.