Also, on more on-topic note, how many people have actually read Reviewing and You? All the way through?
I have. Although every time I look back in that topic, you seem to have added something I don't remember being there the last time I read it. Not that it's really significant, because, well... I don't think I've ever posted a single review to anything on PC. Oh, wait, I reviewed an old version of MKD sometime a few years ago, didn't I? Outside of that, though, pretty much nothing. I don't even really go to the main Fan Fiction forum. Which makes my presence here kind of odd, but whatever.
That said, I had a reasonably comprehensive philosophy on reviewing before reading it, so it didn't change much about my reviewing. It's a good guide, though.
Would you say a review for a story that was entered in a challenge/contest would be different than a review for a non-entry story? Does it depend if a challenge/contest has some sort of criteria on how the stories will be judged? How would you review for a challenge/contest?
Well, there definitely is a difference. Normally, when you review, you are doing it specifically for the author. When you're a judge reviewing contest entries, on the other hand, you're primarily doing it to determine which story deserves to win the contest, and although you should also try to help the author, that takes second place.
Thus, I'd say a contest judge review should focus more on detailing the good and bad points in the story and less on providing suggestions for how to fix it (there should probably still be some of that, of course, but you should not go into elaborate detail on how something ought to have been worded, or correcting individual instances of spelling/grammar mistakes, or something like that). There should also be more of a focus on how the good and bad points outweigh one another and the overall impression of the end result: in an ordinary review I tend to comment a lot on individual parts (this was not well worded, the writing in this scene was particularly effective, this sentence is confusing; this character is fascinating, so is this one, this one is kind of bland) but if judging a contest I'd mostly speak of overall impressions of each aspect of writing while mentioning parts that might be particularly noteworthy examples of what I'm saying (there were some strangely or confusingly worded parts, but also scenes where the writing worked very well, such as this one; most of the characters are well written, but this one feels lacking in comparison). As mentioned before, it is also nice to compare the entry to other entries in the contest to give a better idea of why you placed the entries as you did.