Spell check! This should be obvious, but utilize your software's spell check and proofread your resume for errors. If you're applying for a position where you'd be responsible for written documents, and your own resume is filled with errors, you won't get invited to interview for the position.
Be consistent with your verb tense. I recommend using past-tense, as the resume will then read as a list of things you've accomplished or achieved, instead of your duties. Use action verbs like developed, resolved, reorganized, achieved, and so forth.
Be specific. Use numerical measures to demonstrate achievements as often as possible.
Tailor your resume towards each specific job. Read the job description, and adjust your resume accordingly.
Ditch the objective statement. Apply for specific opportunities and make sure your resume demonstrates your appropriate skills and accomplishments.
Don't be creative with your font types, font sizes, or page layout. It's distracting. Make sure your resume isn't too busy.
Double check your contact info, specifically your phone number and email address.
Make sure your email address isn't unprofessional or potentially discriminating. It shouldn't include your birth year, your graduation year, or how attractive you think you are.
Leave off your physical address, as employers may hesitate to interview someone who isn't within what they'd consider a reasonable commute.
Only include your interests that are relevant to the job you are seeking. Don't include work with controversial organizations (political organizations, religious affiliations, etc.). Leave off unnecessary personal information (date of birth or ethnicity).
Don't use personal pronouns. ("I" or "my")
Use keywords to optimize your resume for Applicant Tracking Systems. (ISO 14001, RCRA, SWPPP, HAZWOPER, etc.)