Characters (Backstory, voice, motivations, behavioral and psychological patterns)
Cut useless or weak parts
Setting (Vivid details, impact on characters)
Scenes (Stakes, motivations, tension, surprises)
Look for plot holes, repetitions, incoherencies
Vocabulary is appropriate, descriptions are fluid and vivid, dialogues are natural and in the voice of the characters.
Rhythm, sentence structure, coherence, narrative voice, not too many adverbs, cut useless words.
Grammar and format
Spelling, verb tenses, manuscript format.