Learn 40 words a day, spend one day revising the vocab you learned every week. Do a letter every day, come up with answers in English, than try find a rough German translation of the phrase you are using. Learn a couple of the phrases you used and just continue practicing writing skills. Try use oral phrases in the letter too.
Do one to two reading comprehensions a week. Study some grammar a couple of time a week- maybe two grammar exercises from the paper, a couple from your book and learning irregular verbs etc.
Do one to two listening comprehensions a week.