* Do your homework. Look up your company's policy on flextime, and ask coworkers who've negotiated it for advice. How did they sell the idea?
* Put it in writing. Arrange a meeting with your boss to discuss your proposal, but also bring your pitch on paper -- and be specific. Do you want a compressed workweek or a daily 8-to-4 schedule? Explain how you'll prioritize to get your work done: You'll still meet with clients during normal business hours, for instance, but you'll fill out paperwork before or after. If you have responsibilities that need to be covered while you're out, identify a coworker who can pinch-hit and explain how you'll "repay" her.
* Stay accessible. Assure your manager that you'll check messages and e-mail from home regularly, adjust your schedule to attend important meetings, and put your hours on your office door and voicemail greeting.
* Show it's a win-win situation. Explain that you'll be even more committed to making sure your work gets done while managing flextime and that your boss gets to keep you -- a loyal employee whom the company has already invested in.
* Sell yourself. Highlight your past accomplishments and dependability. Your value to the company is the main reason for approving your proposal.
* Request a temporary run. If your supervisor isn't sold, suggest a tryout period of six months; you can meet for a review afterward.