In trying to copy from the Writing correction area of The Linguist web site I ran into problems with HTML text. The result looks a little messy. I am sorry. However, this text is interesting in that it deals with the issue of grammar based learning as opposed to context based learning.
Context based learning means reading and listening to interesting input and studying meaningful words and phrases, regularly writing and reviewing one’s writing, and speaking. This will lead to better results than studying grammar, defining parts of speech, trying to remember rules, deliberately preparing for standardized tests etc.
Writing can be particularly useful since it forces the learner to think and to review what he or she has expressed in the new language. Until the learner is quite fluent, the written and spoken language should be as similar as possible. Only at a later stage should they diverge, with the written language becoming more sophisticated and the spoken language becoming more casual. That has been my experience.