QUESTION: I want one of my characters to be a boy from England. How do I get the language and vocabulary right?
Like the US, Great Britain has regional accents and expressions, and their language and accent is also affected by class and education so you need to figure out where that British kid comes from and what his social class is before you start your research.
Most writers seem to forget about class and region when they write, and I always snicker when the housemaid is mistaken for a lady, or the Southern character doesn't sound or act remotely Southern or is from the wrong part of the South.
Take care, though, not to be so accurate that your character is unintelligible to most readers.
The trick is to give the feel and rhythm of the language without making the reader scratch her head over the slang and expressions.
The Internet is a glorious place full of resources and the ability to contact people from all over the world so you should be able to find someone to help you with the specific language and sound of your character. Ask around on reader and writer lists or among your Facebook friends for someone from that area. If that doesn't work, do some search engine hunting.
You should also ask around about movies or TV shows that have characters who sound right for the character you want to write. If you can “hear” that character’s voice when you write, you usually won’t go wrong.