I like revision. I find it fun. Though I think I'm a better storyteller than wordsmith, I enjoying fine-tuning the language. I think it matters.
You can read over a manuscript a million times, but you get diminishing returns, so I've adopted a number of techniques that allow me to view my manuscript differently at different passes. Here are a few of them.
1. Make a couple of "to be" passes
Some people think that any use of "to be" is passive. It's not. Passive means that the sentence has been structured in such a way that it pretty much removes the subject. It's used by slick types to avoid responsibility, and used by scientific types to connote objectivity. Example:
"It was done to prevent catastrophe."
"I did it to prevent catastrophe."
Passive sentence structure isn't great for fiction. But the use of "to be" is more insidious than that. The reason that the use of "to be" should be questioned even when its use isn't passive is that it is pretty much always a case of telling rather than showing.
"He was tall."
"He ducked under the doorway when he entered the room."
In the first sentence, the reader is being told that a character is tall. In the second, they're drawing that conclusion on their own. That discovery makes it seem more authentic. Now, obviously a person being tall doesn't stretch credulity, but the phrasing is also more lively. I don't think "to be" should be entirely avoided, but I don't think it's a bad idea to consciously question every use. So, if your piece is in past tense, use Find to look at every use of "was," then "were." If it's in present, add "am" and "are." It's time consuming, but the end result can be a big improvement.
2. Examine one sentence at a time
It's really easy to get caught up in your own story. Because you understand the context so well, this can lead to fixing problems in your head before you're even aware of them. One way to solve this is to only look at one sentence at a time.
This can be difficult to do without aid. One trick is to highlight a sentence at a time. In Word, you can enable a keyboard shortcut for some hidden commands, but it requires that you let up off the key every time. I prefer to hold the Alt key down as I arrow forward or backward, so I created macros. Instructions for doing both are described here: http://wordribbon.tips.net/T010275_Selecting_Sentences.html
If you go the macro route, you still have to assign keyboard shortcuts to them the same way you would a hidden command.
Going through your manuscript backward one sentence at a time is the ultimate way to avoid immersion in your story, allowing you to focus on language. But a pass going through forward is also a good idea, as it lets you catch problems such as agreement that are much harder to notice going backward.
3. Read your manuscript outside of your word processor
It's amazing how many mistakes slip by when you read the work in the same setting you wrote it: in your word processor. It used to be that to get a fresh view, you had to print your manuscript out. Now you can put it on your e-reader. If you have a kindle, just email the manuscript to firstname.lastname@example.org and they'll email you an .AZW file back. It's not going to be perfectly formatted, but that's not the point at this stage.
I perform this step late in the process, and I just highlight errors as I go. Once I've gone all the way through, I can do a search on my manuscript in Word for a few words of a phrase and go straight to the problem area.
4. Listen to your manuscript
Because you know what should be on the page, it can be difficult to see what is on the page. Most of these tricks have dealt with seeing your manuscript in a different way, but the ultimate change is to hear your manuscript.
There are some free programs you can use, but I like to use the text-to-speech function of the Kindle. It's the only time I use it, but damn if it isn't the ultimate author's friend. No matter how familiar you are with your story, if you typed "shitted on the ground" when you meant "shifted on the ground," you're going to hear it (yes, that was an OCR problem, but it's hilarious!). When you hear a problem, just pause with the spacebar and highlight the mistake.