in summary, the main things i try and focus on are varying the tenses used, consciously trying to use every one i know. also, i know it sounds simple but learning crucial vocab and making sure u know the genders of important words, because any mistake is a mistake, no matter how simple it is.
also, having a vew random but significant and relevant facts to throw in every now and then is useful. it seems that a great proportion of marks in the oral (around 30%?) are actually given for something like the ability for you to respond, i.e. just answering the question without hesitation or delay. good luck.
i got an A btw, (81/90 i think)