"My girlfriend invited me to go to New York with her next week, for a conference. It's a great opportunity and I really want to go! Can I ask for the time off this close to the date?"
One of the biggest challenges in establishing yourself as a professional with a solid reputation is how to juggle what you reaaaaaallyyyyyy want to do outside of work, with what your workplace needs and wants of you. "But it's my life, I should be able to do what I want," you think, while your boss is thinking "it's our busiest time of year, is he blind? If he asks for one more day off I need to hire someone more reliable."
You really don't want to be slapped with the "unreliable" label, because you have to work way hard to get rid of that once you have it. It's much easier to just not get to that point than it is to recover from that position when you're in it. If you can build a reputation as someone who works hard and is consistent, then you'll earn the flexibility and grace to do what you need and want to do outside of your work, and it won't be a problem. But you have to protect your workplace reputation like gold. Here are some strategies that might keep you out of hot water and keep you in a position where your reputation is stellar.
Do your homework. Asking for time off? Check calendars and what you know about your workplace's rhythm and schedule to anticipate conflicts before you ask. Do people around you seem busy? Do you notice that calendars are full? Does your calendar appear to have conflicts or meetings or events or deadlines that are close to or conflict with what you're asking for? Are there standing needs of your business that might be impacted by your request? Collect some information as you get ready to ask for what you want.
Solve any problems. Anticipate objections to your request. What are the common reasons that other peoples' requests are rejected or approved? If you're asking for a flex schedule, anticipate as much as you can all of the reasons your boss would say no to that, and then proactively propose solutions to those objections when you make the request. Unable to be part of a project or event or another obligation? Develop a plan for how your responsibilities will be met to show that you have already thought through the solutions to the problems your request might raise.
Be careful what you ask for. There is an adage that says "it doesn't hurt to ask", but sometimes it actually can. Your boss doesn't want to say no to you, (no one likes to say no!), and you want to make it as easy as possible for people to say yes. Sometimes this means not asking for things you want, in order to save up some political capital for things you might want to ask for later that are more important to you. Think before you ask. How important is your request to you? Are you willing to use up political capital in order to make it happen? If so, go for it! But if not, save it.
How will this benefit them? People are more likely to say yes to you when there is a benefit to them, or is something that they value as well. You want to make your requests win-win as much as possible, and if you can't, at least make the impact neutral. Think about ways your request for what you want might enhance the company's goals, your boss' goals, or ties into company values and priorities. Be sure to cite those when you ask.
Prepare. If you know you're going to be asking for something big in the future, you can prep by making sure that you're nothing short of a star performer before you ask. This greases your reputation a little bit before you actually submit your request. Thinking about asking for a flexible schedule where you arrive late and stay later? Stay a bit late consistently over the next few months to show that you have the track record to pull that off. Going to be asking for a change in responsibility? Look for ways to demonstrate extra responsibility and trustworthiness now, before you ask.
Think about what's important to you, be mindful of your reputation as a professional in the workplace, and THEN make your request. Your boss will be so much happier, and you'll make it that much more likely that you'll hear "yes".