Either because you're shy, you're short on time or just nobody likes you, sometimes having a second pair of eyes read your work isn't going to happen.

So sometimes you have to do it yourself. This article from Absolute Write has some good tips in it, such as:

"Putting your work away for a while-- sometimes weeks or months-- can allow you to come back not so enamored by it."

and

"Organize your notes from 'easiest' to 'most difficult.'"

The article also recommends getting a group of actors to read your piece out loud, which might be a little unfeasible. But read it out loud yourself. It might be a basic bit of advice but it works every time (and I'm always amazed by how lazy I am, reluctant to just open my mouth and read my stuff.)

I've also picked up a few good tips from other writers, including keeping an eye out for needless details (too many meaningful looks and glances) and using the word "as" in place of "while". I learned those from a class with this guy and you'd be amazed how much that pops out at you once you start thinking it.

I also learned from a seminar with this fellow a great but time-consuming way of checking the quality of your words. Go through your piece and circle all the verbs. Then go through and underline all the nouns. Examining what you use can help you see what gets repeated, what's weak and what can bring out more meaning in the piece.