Having just returned from my very first solo travel experience, here are some things I wish I had known before leaving:
1. Plan, plan, plan. I'm a very laid back person and when you're travelling with a group of friends getting lost on the way to your hotel, missing a boat, or getting stranded in a foreign city all seem like exciting adventures and so I usually don't feel the need to plan out every detail of a trip. These things are markedly less enjoyable when you are travelling alone so make sure you plan out where you're going to go and how you're going to get there, rather than just winging it.
2. Budget carefully. Unfortunately, a lot of things in this world were built for two meaning hotel rooms are likely to be much more expensive if you're staying in them alone. Hostels are a good alternative. Personally when I'm alone I would prefer to stay in a hotel unless I could find a safe and reputable hostel in a central location (I have stayed in some horrific places in the middle of no where with friends and they are definitely not places I would be comfortable staying alone!). Especially if you are going somewhere off the beaten track, some of the cheaper hostels can often end up being fairly quiet making the experience even eerier. This is just a personal preference as a female traveller, but I would recommend thoroughly looking in to the location and reviews of anywhere you're going to be staying.
3. Print out walking maps before you arrive in your destination. This is definitely something I would never normally take the time to do, but you may find your phone doesn't work, where you're staying doesn't have wifi and the language barrier is extreme. In which case, knowing where things like internet cafes, supermarkets and attractions are from your hotel can be incredibly helpful.
4. Speaking of the language barrier, do research on the local language. It's always a good idea to take a guide book and learn a few key phrases so you can at least greet and thank people, but make sure how likely it is you are going to be able to communicate with people at all if you don't speak the language. In many European cities you will be able to communicate with shop owners and waiters in English, in others you will struggle. For example, I naively assumed I would be fine in Rome not knowing any Italian but there were many restaurants we ate in where I would not have been able to order if I hadn't been with an Italian speaker. Make sure you know these things before you go and plan accordingly.
5. Remember you don't have to accommodate anyone else when you're travelling alone! Don't like museums but always visit them because you're used to travelling with an art lover? Skip them! If you get to a city and decide you want to spend your days wandering around, enjoying the sunshine and eating and ditch your itinerary, then do it!
6. Most importantly, don't be afraid to try things just because you're travelling alone! If you meet a group of tourists in your hostel and they invite you to a bar crawl, go! (if you want to, obviously). Don't be afraid to try nice restaurants, spas or anything else because you're alone either. This was a silly worry I had before travelling alone, particularly eating in restaurants by myself but I noticed there were usually a few other people eating alone, often reading a book. I had honestly never noticed other solo travellers before I travelled alone!
Hopefully I will be taking another trip in the near future and I will definitely try to plan (and budget!) it better next time. Overall travelling alone is a great experience and perhaps equally enjoyable to travelling with friends.