I got an agent for my contemporary YA when the word count was almost 90,000 words - about 30,000 words longer than the 40-60,000 words usually recommended for the genre. In the first round of submissions, editors said it was too long, and I had to cut it by 20,000 words. After we sold the book, my new editor said it was still too long, and I had to cut it by another 10,000 words. Now it's just over 60,000 words, just about the average length for the genre.
What to take out of this? I'm not sure. On the one hand, I feel like you're probably going to have to do the work of making it the right length anyway, so why not do it now? On the other hand, I really believed my book was as short as I could make it, and it's only when I had what I felt were strong outside incentives that I found it in myself to cut it.
That said, I told myself each time, I'm going to cut the word count, but if I don't like the results, I'm going to stick with the original - but in both cases, I found myself liking the shorter version *much* better.
One thing I would say, although I did reduce word count partially by getting rid of unnecessary words and phrases, I also found I had to be willing to think about the plot and reconsider every scene - did this further the story? Did it convey absolutely necessary information? In many cases, I identified the important parts of individual scenes, took out the scene entirely and incorporated the relevant info elsewhere in the book.
It was a lot of work, but definitely worth it.