(Yes, I know I'm NOT supposed to be my own critique partner. Yes, I know I'm supposed to meet other writers and get their opinions. And yes, I am actively on the hunt.)
Step 1. Figure out what you want. For me, its questions. I like it when someone writes in the margins things like: Would she really say that? Maybe she says it, but does she believe it? Did he get caught on purpose? Why do they trust each other so easily?
Questions are good because they help me draw out the story within, instead of throwing other ideas on top of it that don't fit. Sometimes a reader will have a really good idea, but often times its nicer if they just point out the issue and leave it open ended for me to decide.
What is your dream critique partner like? Does he scrutinize your dialogue and act it out to show you its faults? Does he amp up the action?
Step 2. Print out your WIP. Print it out! Do it on paper. I don't care if you're a child of the digital age. I don't care if you've been typing since you were five. Print it out.
Step 3. Be your dream critique partner. (Did I mention that my dream critique partner also likes to sit in bed and eat ice-cream while reading? Lucky me.) Do the things that your dream critique partner does. Ask yourself questions. Question anything that is weak or easy or convenient. Tell yourself its too long. Tell yourself you don't need that part. Tell yourself that people don't talk like that.
It's simple really. It's just like life. "Decide what you want to be and go be it." --Avett Brothers