1. Make it easy for your boss to say yes. If you come to your boss with a proposal that's only partially thought-out or one that would require significant work from her or others before it could move forward, you're presenting obstacles to a "yes." Another obstacle is being unclear about exactly what you'd like her to approve: If you simply say, "I'd like to find more ways to be involved with our strategy planning," she will have to figure out what those ways could be. But if you say, "I'd like to attend the team's monthly planning meetings," you're giving her something specific and easier to OK.
2. Get the timing right. If your company is in the middle of cost-cutting or your manager just got reprimanded by her own boss, now probably isn't the time to make a special request. Make sure you're considering the full landscape that your boss is dealing with before you make your request.
3. Lay out the business case. Your proposal should explain what's in it for your company, not just for you. So for instance, if you're asking to telecommute on Fridays, don't just explain that it will make it easier for you to pick up your kids from school. It's fine to mention that as context, but you should also point out that you'll get more done because you'll be working during the time you'd otherwise be commuting and will end up putting in more hours than if you were working in the office.
4. Show that you've thought of pros and cons. If you only lay out the reasons in favor of what you're requesting, you'll leave your boss in the position of having to think about and point out the disadvantages. But if you make it clear that you've thought through both sides and clearly understand the pros and cons, your credibility will increase and your argument will be stronger. Related to that…
5. Preemptively offer solutions to the downsides. If you don't acknowledge the downsides and offer solutions to them, you'll leave your manager to resolve those concerns herself, which makes your request less likely to be granted. So, for instance, if you're asking for a training class that isn't in the budget, you might point out that two specific skills you will gain from the training will save the department from hiring outside contractors in the future.
6. Understand the answer might need to be "no" for reasons that have nothing to do with you. Managers sometimes have to turn down reasonable and worthy requests because they have to deal with three more pressing requests first, are restricted by bureaucracy above them or can't grant your request without granting five similar ones from your co-workers. Taking the same broad view that your manager has will help you better understand a "no" if you get one, and it can also help you craft a better proposal to begin with.
7. Ask for an experiment, not a lifetime commitment. If your boss seems hesitant to grant your proposal, ask for a limited-time experiment, such as trying telecommuting one day per week for a month and then revisiting it at the end of that time. An experiment is much easier to OK than a permanent policy change.
8. If the answer is ultimately no, find out what it would take to change that. You will sometimes need to accept a "no," but it's reasonable to ask about what could make that answer different in the future. For instance, if you're turned down for a raise, ask what you'd need to accomplish to earn one. Or if there's not money in the budget for new software now, ask when you'd need to approach her by to get it into next year's budget.
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the co-author of Managing to Change the World: The Nonprofit Manager's Guide to Getting Results, and former chief of staff of a successful nonprofit organization, where she oversaw day-to-day staff management, hiring, firing, and employee development.