Practice your writing skills on the British Council’s site. There are four levels of difficulty, starting with introducing yourself on a blog (level A1) to writing a movie review (B2).
One particularly useful page is about writing more formal e-mails. This one is from level A2. The activity starts with a typical exam question, gives you some tips, and then asks you to do some interactive tasks.
The British Council site has many things to offer, and I don’t want to overwhelm you, so I’ll introduce them little by little.