The Academic Word List is an essential vocabulary list of the most common words found in academic texts. A copy of the list can be found here.
This list is essential because it gives you a guide as to which words you should aim to include in your academic writing. However, as with all wordlists, these terms are best learnt and used in context.
Step 1: Learn the words in context
I think Quizlet is a great little tool to learn IELTS vocabulary fast.
Step 2: Review your existing essays
Start by writing a normal task two essay question, then go through looking for opportunities to improve your existing words:
Generally speaking, a healthy forward looking university is said to have dynamic well funded faculties and hard working students.
Generally speaking, a healthy forward looking university is said to consist of dynamic well funded faculties and hard working students.
This small improvement lets the examiner know we have a more advanced vocabulary, and would help to boost the lexical resource criteria of the test.
Step 3: Get feedback AND self correct
Find a native English speaker (or someone of similar ability) to read through your work and show you where you went wrong and what can be improved. I would recommend an essay correction service or use your current English teacher. Before this step, first try yourself to correct your work, this way you can identify errors on exam day.
Bonus Resource: The Academic Collocation List (ACL)