Don’t over-use linking phrases. Use them sensibly where they are needed.
Don’t try to be clever by using more unusual words and phrases, you’ll probably misuse them and get a lower score.
Don’t use the same phrases again and again. Don’t try to learn long lists of phrases because you only need a few for your answer in the test. The examiner is looking for a variety of phrases, so just make sure you keep it simple. Don’t confuse words and phrases that link ideas between sentences or paragraphs with those that link within the same sentence.