Note the title. Tricks, not tips, because the following isn't the Holy Grail of Revising Secrets (though if someone has a copy, send me a message and we'll negotiate a price). The following is simply things to help fool your mind when it's become a weeping pile of mush from countless hours spent revising.
Read from a different character's point of view
This is especially helpful on dialogue-heavy sections to ensure each voice is solid and each exchange is easy to follow.
Read something else
A book, a newspaper, the fine print at the bottom of a sales receipt. Anything that will allow you to shift gears. Getting your brain on a different course is like a splash of cold water to the face.
Not permanently, of course. But if you've already put in some serious time on a certain WIP and you're reaching the I-hate-you-but-I-love-you stage of revising, it doesn't hurt to work on something else. You're not giving up on it, you're taking a step back to evaluate and clear your head. When you return, you'll have a fresh perspective and be able to fall in love all over again.
What tricks do you have for revising? List 'em in the comments below!