There will come a stage when you know it has to spend time in the deep freeze before you can see anything new. But let's talk about that raw first draft. Read the whole thing through, jotting short notes as you go, not attempting to tinker with specific problems right now. What you are looking for, in this first read-through, is faults in consistency, pacing, connections, and drama. Faults in these areas have to be solved first before you tinker with the language.
Consistency covers many things.
You might have an inner-city gang member forget to speak in slang. This leads to pacing. Styrofoam does not nourish the reader. It is boring. As you read through, mark the passages every time you became impatient or bored.