You're the best person to write your résumé but not always the best to edit it. Are you communicating your work experience as effectively as you could be? Ask yourself the following three content questions to see.
1) Are your bullets in priority order?
Your list should go in descending order of importance, so that your document can be easily scanned. Ask yourself: Is this the most important job task I did? Then, add your next most important responsibility. Remember that the writing style should be short, action phrases reflecting the appropriate tense (past or present).
2) Do your descriptions have any numbers?
Quantify by adding numbers into your entries whenever you can. Paint a picture for the reader so that they can easily understand the breadth and depth of your experience. Some ideas include: company size, project scope, budgets, task efficiency, sales, customer interactions, fundraising, and task hours.
3) Have you condensed your job duties to the most important ones?
While it's tempting to take your job description and transfer every responsibility, that lack of editing will hinder the reader from quickly scanning your best content. Eliminate any obvious job duties--those go without saying.
*Bonus Tip: avoid vague phrasing, like mentioning that you're a team player or that you have excellent communication skills. Instead, prove it with your descriptions and numbers (e.g., published monthly newsletter articles on group dynamics and team performance).
The purpose of a résumé is to summarize your best, most relevant work experience. Make sure your content PROVES your qualifications.