Dear,friend(这里写那个人名字)
I'm glad to receive your letter and happy to know that you will go abroad next year.You will have a totally different life in the future.
In your letter,you asked me how to learn English well.I will tell you,practices makes perfect.To learn English well,you must practice more.
Let’s start from oral English.Since you will go abroad,speaking is rather important,for you must communicate with others in English.You can speak with your friends in English.You can also go to English corner to practice your English.
Knowing more words is also important; you can buy a word list book.There are many useful words in it.You can bring it with you no matter where you are.When you have time,open it and try to remember the words.
Besides,reading English newspaper can improve your reading skill.You can buy China daily,and read whatever you like.This method can also improve your interest in learning English.
I hope that these advices can help you!
Good luck
Yours sincerely,你的名字