Keep on doing writing tests after tests. You must write minimum 100 tasks each in Task 1 & 2 before appearing your exam. Daily 1 or 2 writing tests would be adequate. Correct your Grammar wherever necessary on task 1 & 2 completion. Get rid of normal words i.e., replace your accustomed vocabulary with correct terminology / lexicon / glossary with suitable thesaurus ( check in online itself).
Make note of the vocabulary in excel which you use and replaced one in the test and revisit it daily. Apply those vocabulary in the subsequent tests. See the result (your confidence level) of your 100th test. This lasts through out in your life and easy way to crack the exam
Patience and Time is imperative.