ELT Lexical Syllabus/Frequency lists

Unfortunately, you probably need to know about 95% of the words in a text to be able to get a good sense of what it's about. This leads to some advice for language learners:
 * 1) it will be better to try reading simplified texts
 * 2) it is useful to concentrate your study on words that are frequently used

Cambridge ESOL has published a list of the words that belong to the levels "Basic User" and "Independent User". Lists of words organised according to how frequently they appear are available from Kilgarriff's website.