Top Tips for Solo-Traveling Europe:

Europe is a magical region of the world that is rich in beauty, architecture, and culture with some of the finest cuisine. It is also significantly more travel-friendly due to the abundance of public transportation and hostels; Europe's infrastructure almost seems to be designed with travelers and backpackers in mind. 
Not to mention, America is statistically far more dangerous than Europe for the simple fact that many officials (police) do not even carry guns! But that's another topic...

Stay in Hostels, Skip Hotels: Hostels are ideal places to meet fellow travelers while also a small fraction of the cost. If you are traveling solo, hosteling is the single best way to meet people organically and non-awkwardly. Plus, if you only speak English (like me), you're bound to meet others who can steer you in the right direction. Just remember to bring a TSA-approved lock for locking up your belongings.

On that note… Choose your hostel wisely: When traveling solo, the type of hostel can really shape your overall experience; not all hostels are created equal. If you are looking to meet others abroad, choose a hostel that offers daily walking tours and/or nightly pub-crawls. On the morning walking tour, you’ll naturally meet someone who is suitable to go explore with or have a few drinks with later that night. I’ve found the more touristy hostels to be better for meeting people, and safer (but doesn’t mean you have to stay in the touristy area). For cheap rates and solid reviews, I recommend the Hostelworld app.

Stay in control, don’t get too drunk: Although this is something to always bear in mind regardless of your proximity to home, becoming too intoxicated while alone overseas usually does not end well. Becoming too intoxicated makes you an automatic target for pit-pockets, being ripped off, and just represents yourself and your country unfavorably. Losing an important item such as your passport, wallet or hostel key can also put quite the damper on the fun, which defeats the main objective, right? 

Travel Lightly, Hold on Loosely: Whatever you do: Do. Not. Over-pack. The first time I went overseas I brought my entire wardrobe with me in a massive suitcase. The second time, I went for the same amount of time except with only a 40-liter Osprey backpack. Everything in life is temporary, which is especially apparent whilst traveling. Travel lightly, don't take anything too valuable or sentimental from home with you on your trip. Fill your bag only halfway to three-quarters so that there’s ample room for the novelty items and a few souvenirs along the way. Remember: it's the memories you make and the people you meet that shape the experience, not the material possessions acquired.

Be aware; respect cultural and communication differences: Oftentimes, privileges are most likely to be abused inadvertently- by one simply not being aware of them. As Americans, we tend to be spoiled and expect instant gratification. The food may take (way) longer at a restaurant; customer service is not as speedy as you may be used to (Europe tends to generally be slower-paced). In general, don’t talk about political views unless asked, and do not say anything derogatory about their country, even if it doesn’t feel offensive to you. Try to refrain from saying “Well, in my country…” I made this mistake when complaining about the lack of hot water at my flat in Ireland. 

Do your research beforehand: Although spontaneity and going with the flow is generally a great thing (especially when traveling), it never hurts to brush on up on the history of whatever city or country you are planning on visiting, as well as points of interest. Americans are notoriously known for being bad with history (including myself), so having a general basis of it will earn you a few brownie points and be taken more seriously (i.e. prove you are not an uncultured American). On that note, it also never hurts to brush up on some geography if the last time you looked at a map was in grade school.

Sign the back of your credit card: Yes, they still actually check the signature on the back of your credit card in many places in the EU. When I was at a supermarket in Berlin, the cashier refused to take my payment because she said it was not valid unless signed... even after I offered to pay in Euros. More notably, this was probably the only rude encounter I experienced throughout my entire 3-month backpacking trip. Although this is uncommon in "cashless" countries like Sweden or London, it’s better to be safe than sorry (and embarrassed).