Don’t despair if, at the beginning, you hardly understand a thing! Soon you'll see how little by little you are getting more. Try to avoid resorting to using English... some of your classmates and teachers won't understand you and anyway you are here to practice your Spanish.
You might want to use our multilingual glossary on the web or other online dictionaries but do try to guess at the meaning of a word with your teachers’ explanation first: it will be better for your learning process and it’s more polite!
Don't be scared of just jumping in and making a fool of yourself. Your main aim is to interact with Spanish people and to do this you have to understand and make yourself understood. Try and apply your new knowledge to real life situations from day 1. Don't panic! Spaniards are quite patient and don't usually laugh their heads off at new learners' mistakes (well not that much anyway!).
You should be learning new vocab for at least 30-60 minutes a day - bear in mind that you'll be on 400 new words per week at the beginning. Knowing the words makes speaking a lot easier. Lots of learners concentrate too much on grammar. Learn vocab by theme rather than alphabetically and try to translate into Spanish rather than the other way round, where possible writing the words down with accents instead of just speaking them. Some words will be a lot harder to learn than the ones which have a root in your own language. Separate these blighters and make a special black list.
Accept gracefully that Spanish is very different from your own language and avoid searching for too many parallels early on: these will help later but will complicate things for you now.
When you're doing your grammar exercises make sure you understand the whole sentence. Don't be lazy! It's quite possible to fill in the gaps correctly but you are missing the point if you are missing the meaning.
Learn expressions related to asking about your Spanish learning as soon as possible like "What does ... mean?", "Is ...right? "How do you say ...?","Which word means the same as ...?". You'll get an explanation which you can decode in your head and will thus have substituted dictionary page-turning for a much better speaking/understanding information-gathering model.
(Later on) watching movies in Spanish with subtitles in Spanish is a great idea as is reading newspapers, easy readers, watching the news or other interesting programs, listening to the radio and above all, talking to Spanish people. Living with a family will give you an instant leg-up as you will have to speak Spanish every day at home.