If you end up needing to make a Genius Bar reservation, it's usually because a piece of Apple hardware isn't working at all, so the appointment can be stressful. When you have to make that appointment during peak shopping season, that stress can be compounded. Here are a few tips to make that appointment as smooth as possible:
First, try to not to even have the appointment. Try some of the battery life tips we've suggested in the past, or try a completely clean install and see if you still have trouble. Take note of what you tried and the results in case you do have to go in. There's a big difference between "It's broken" and "My iPhone crashes randomly, it's been happening for about a month even after a factory restore and no additional apps installed." One of these takes a long time to walk through, the other one heads straight to diagnostics portion of the program and starts the actual determination of a plan of action.
If you don't have any luck with basic troubleshooting, take a deep breath and walk through backing up. Once you have good backups, you can schedule the appointment before you leave for the store. There have been reports that walk-in appointments are sometimes available in some locations, but even if that's a possibility the wait could be much lengthier than if you booked ahead. You can find a store online or you can use the Apple Store App and book the appointment. A bonus to the app is that you can check in when you get there.
Remember, adding a comment that includes what you're wearing is amazingly helpful. If you walk in and check in for your appointment with an employee, that's what they're doing anyway. Which brings the next tip: Be nice. Act like your mom is standing just over there watching the whole thing. Would you want your mom to see you act like an entitled jackass to a retail employee, and at Christmas time to boot? Probably not. So be cool. I don't want to have to say it, but I've been in a few Apple stores in the last couple of weeks, and it (sadly) needs to be stated.
You know how you have all this holiday stress with parties and gifts and events and all of these things to do, and now on top of all of that your Apple stuff is broken? Now imagine you have all that stress and you work at the Genius Bar where sometimes the patient can be saved, but sometimes not. And you have to break that news. Everybody has a lot happening right now, so that ounce of kindness will pay off many times over.
See how friendly they look? Help keep them smiling and be friendly.
Once you're all checked in, look for the area where it seems the Genius Bar action is happening and stake out a spot. If you're there for an appointment it's good to be near where the action is since the person helping you will already be close. If you know you have some time (at check-in someone will tell you what the wait looks like) go ahead and browse, or even wait just outside the store (on the free Wi-Fi) until it's closer to your turn.
When you do get to talk to someone, lay out all the information you have. What you tried, how it turned out, if there's anything you can point to that changed (everything worked great until I installed this app/the battery died/I got struck by lightning) that will also help. Again, be friendly. It's totally ok if you don't have the answer to a question, don't make something up or you could lead the technician down the wrong path.
Keep being nice (I did mention being nice, didn't I?), and with the above tips your appointment can go smoothly even during a very busy time of year.