Directions for a perfect vacation: Part 2

4. Plan out every detail beforehand.
Too much structure? Trust me; ignoring this can cost you. It did me. It really stinks when you're sick to the stomach on a hot day, you have a heavy pack, the hostel is a good mile from the train station (if not more), and when you get there...it's full. No reservations? That's just too bad. You spend half-an-hour on a phone, trying to find some cheap hotel that costs twice as much money--and is another mile away. More hiking. Later you throw up in the hotel sink.
After that situation, I spent a few hours at an internet cafe, making reservations for the next month. Every day planned out.
Make reservations early. Plane flight (the earlier, the cheaper, and we're talking hundreds of dollars). Hotels/B&Bs/hostels (so they don't fill up and leave you stranded). Even a few popular sights require reservations.
Plan what restaurants to visit, what sights to see, how long to spend at each sight. The guidebook I used recommended a pretty suicidal schedule...the Louvre was definitely worth more than the two hours it gave me. Take your time, enjoy the experience, and don't rush it. Don't plan too much in one day.
Be sure to apply for your passport early. It may take a few months to obtain.
Also plan your transportation out early. Car rental? Train? Buses? Have all the details and reservations worked out before you leave. One exception. If you're using public transportation, and are not using a railpass, you'll probably want to buy most tickets in train stations. Exceptions would be for very long train rides, including overnight trains where beds are available. Even these are probably best to buy in Europe, as buying them from the United States can be expensive. Just buy them in advance.

5. See what you want to see, not what the guidebook recommends.
My guidebook recommended Versailles highly. I wasn't impressed. Tons of tourists, but still incredibly boring.
On the other hand, it gave just a slight recommendation to the natural history museum in Vienna. That was one of my favorite sights in Europe. It's housed in an awesome building, and it's practically tourist-less. And, at least to this biology teacher, the museum rocked. Interestingly, a similar museum in London received much higher recommendations, and yet I didn't enjoy it nearly as much; the hordes of people and the cool yet gimmicky dinosaurs drove me off fairly quickly.
If you're seeing the big sights during peak time (May through September), expect crowds. Waking up early and getting there before the tourist hordes is highly recommended.

6. Consider bed and breakfasts.
Hotels are usually comfortable and safe, but they are also expensive...and sterile. You don't get too much of the culture...and culture, hopefully, is one of the reasons you're in Europe. To be fair, some small hotels are nice...I stayed in a good one...but most of them won't help you appreciate Europe more, and they'll cost you big bucks.
If you're alone and on the cheap, hostels may have to do. Some of these are filled with drunken idiots (usually Americans). Many are co-ed (some may have issues with it--I just dealt with it). Most people who stay in these are young and wild (late nights spent drinking). I did, however, meet some great people, including a cute Asian (I forget the nationality) who had a crush on me, and a friendly Scandinavian teenager who, instead of drinking, spent his last hour before an early bedtime listening to music on his headphones. If you're traveling alone, hostels are a great way to meet people. Of course, you'll also have to deal with roommates who come in late, drunk. One of my roommates was an angry gay man from California who snore up a storm. My favorite hostels were the uncrowded ones, or ones where I met friends. Where do you find an uncrowded hostel? Easy. You find it where the crowds aren't. Either they never go there (Karlsruhe), or they all leave for the night (Carcassonne).
Trains can be an interesting place to sleep. Some offer beds (for a decent price). Be warned: the beds are small and bounce around a lot. And they're often piled three deep. Usually, your conductor will wake you up before the train stops at your destination. It's an efficient way to travel...but it's not a very comfortable way. Even worse is not having a bed. There's no guarantee you'll find enough seats to lay down on on an overnight trip. Worst of all? A bus ride overnight. If you think you can handle traveling overnight (other than, of course, the flight in), get a bed. It's the lesser evil. And you won't have to spend long awake hours traveling (although you'll miss out on some sight-seeing from the train).
The best place to sleep in Europe? A bed and breakfast. A courteous host, a great breakfast, a comfortable, homey room. And low prices. As a solo traveler, I only used these when they were on the cheaper side. When I go with April, we'll stay in these every night. I did have one bad experience with these. I arrived in a small German town, walked up to the bed and breakfast, knocked on the door, and...no answer. I hung out for a couple of hours, lugging my pack around and checking the town out, and then returned. A man at the door was telling other guests that his wife had just entered the hospital, and that the bed and breakfast couldn't operate without her. I had to find another room (a little more expensive, but not a big deal). Also, realize that the language barrier is going to be bigger at a small bed and breakfast; hotels and hostels usually have someone around who can speak English, while with bed and breakfasts, you're taking your chances.
Americans be warned. Wherever you stay, you're expected to clean up after yourself. Re-use towels, don't use a ton of water in the shower, stuff like that. Europeans are more conservative...meaning they conserve more. If only the conservatives here in the states did that...