Make sure you know weather and news vocab for the aural, something always guaranteed to come up. My teacher also thinks question words (wer, wessn etc.) may come up in the grammar section. As for the letter, something on 1916, Euro 2016, Water Charges etc may be asked, something relevant in the everyday life. Apart from that, make sure to stuff the Ausserung and letter with idioms and always give as many details in the aural and reading comprehensions as possible.