Rachel Gardner has an excellent post on the topic: "Tighten Up Your Manuscript."
Here’s a checklist of things to consider cutting:
→ Adverbs, especially those with “ly” endings. Ask yourself if they’re necessary.
→ Adjectives. Often people use two or three when one or none is better.
→ Gerunds. Words that end in “ing.”
→ Passive voice: Over-use of words like “was,” "were" and "that" indicate your writing may be too passive. Reconstruct in active voice.
→ Passages that are overly descriptive.
→ Passages that describe characters' thoughts and feelings in too much detail (i.e. long sections of narrative or interior monologue).
→ Passages that tell the reader what they already know.
→ Unnecessary backstory.
And there's more.
Here’s a list of words to watch for. Carefully consider their necessity and effectiveness:
about, actually, almost, almost, like, appears, approximately, basically, close to, even, eventually, exactly, finally, just, just then, kind of, nearly, practically, really, seems, simply, somehow, somewhat, sort of, suddenly, truly, utterly, were.
What she said.