Learning the Local Language
So, first up: you have taken some language classes already, right? Moving to a new country, particularly the European countries where English is not the first language, will go much, much smoother if you speak a little of the language. Even just being able to say 'please,' 'thank you,' or asking how much something costs in the store is a huge help.
Before heading off to Europe to work, it does make a lot of sense to have some experience with the language first. You may take a class in the language, or it may be as simple as using some practice sites on the web that offer free online tutorial for basic knowledge of the language.
Once you are settled in to your new home country, there are all kinds of ways to learn more of the local language. The most obvious choice is to take one or more language classes while you are working in Europe. This path certainly makes the most sense if you are trying to work on a student visa, or if you are working as an au pair. But this formal method is certainly not for everyone. Keep in mind that you are surrounded by people you can speak with to practice; make use of that.
One possibility is to join a community group that has similar interests to yours. It might be the local hiking club or the local quilting club; either way, you will be able to do an activity you enjoy with a bunch of like-minded people while you practice your new language. Since you will be exchanging ideas on a topic you both enjoy, many more people will be willing to put up with and help you with your halting speech since they are also getting something out of the exchange. The internet is your best friend for finding these local clubs, but don't forget to check out local bulletin boards at community centers and churches as well.
Another possibility is to volunteer to teach people English in exchange for them teaching you the local language. Put up some flyers at the local community centers, churches, and markets to find some interested people. This approach will take a bit of leg work and some patience before you find some people who can help you as much as you help them, but it's also a great way to meet a bunch of new people who are not from your workplace.
Finally, you can use the local expat community that you will surely be spending time with during your stay in Europe. While expats may not be the best for practicing the language with, they are perfect for asking the meanings of specific words, or to clear up some grammar confusion. The best way to use this resource is to make sure you learn something new about the language each time you meet with your expat friends. Then, over the course of the following days, you can practice what you have learned in all your other conversations.
Even if learning a new language is not a high priority for you, use this fantastic opportunity of living in another country to pick one up anyway. Immersing yourself in a language by living in that country is the best, and fastest, way to learn a new language. Set some realistic goals for yourself for how much you want to learn and dive in. The goals that you set will be dependent on how much previous exposure you have to the language and how long you have to spend in the country. Perhaps your goal will be simply to be able to have a conversation with a local by the end of your stay there.
Because of the cosmopolitan nature of Europe, almost every single person you meet, particularly in the cities, will speak at least some English. This is both a blessing and a curse for you. On the plus side, even strangers will be able to help you practice; you will be able to speak in the local language while occasionally using an English word and you will still be understood.
On the minus side, many people will sense you struggling with the new language and simply start speaking to you in English to make things easier for you. You will find that there will be many times when you will have to politely ask people to keep speaking in their mother tongue rather than English so that you can practice.