When you're editing your manuscript, there's an essential list of tools you're going to need:
1. Your Manuscript
2. Coffee/Tea/Caffeinated Beverage of Your Choice
3. Chocolate, or any other such kryptonite
I say music and movies, but only if you need background/white noise. My roommate sometimes gets irritated with me because I'll have a movie on the television, and have earphones in (or my music will be blatantly blaring out from my laptop).
Make sure you're in a comfortable environment for yourself. You won't be able to concentrate properly if you're concerned with lots of people around you, or even vice versa, if you're the type of person who needs a busy atmosphere.
Something else I'd suggest: if your manuscript if on your computer, print it out. A physical copy looks and feels much different than electronic. In the same kind of theme: try posting a portion of it in the body of an email, in a Facebook message to a friend, on google docs. When you put your work in a different context or layout, it looks completely new, so it helps your eyes catch things that you might otherwise miss.
Also: if you're using a paper copy, use your favorite color of pen. It might sound weird, but seriously. If you love the way red looks, then use it. If that red pen intimidated you, switch it for pink, or purple, or orange. Stay away from blue and black, though; you want something bright that you can see easily.
Remember to take breaks, as well. If you've been editing for three or four hours straight, take at least ten-fifteen minutes to get up and walk away. Make some food, refill that coffee cup, go for a walk or take a trip to the gym. Keeping your mind refreshed is crucial. To go back to that paragraph on the atmosphere: sometimes a change of scenery can get you jump-started, as well. Even if it's as simple as moving from your living room to your bedroom, or as complicated as your house to a coffee shop, a change of surroundings as you edit can help, as well.
Note: editing is supposed to be messy. It can also hurt. Lock up that part of you that loves your baby, and let out that wild, critical monster with the scissors who wants to rip your story to pieces. Once you become comfortable with cutting and changing things, it'll get easier. It'll still be messy, but it'll be easier.