The mere fact that you're asking for a change in your working arrangement or schedule presupposes that the change is going to work for you. So when proposing the change to your employer, rather then focusing your presentation on all the reasons the new arrangement is important to you ("My dog really needs me. He gets very upset when I'm not home."), focus instead on the business implications.

Look for the business benefits of the new arrangement. Perhaps the working hours you're seeking as part of the flextime arrangement enhance you company's ability to serve its customers. It's possible, too, that by telecommuting several days a week, you can free up additional office space.

Be careful, though. More often than not, your benefits from any alternate working arrangement outweigh the company's advantage. Be sure you can convince your manager that the change in working arrangements isn't going to impede the company's ability to achieve its strategic goals.