With every new unit, write or type out a list of all the words, their meaning, and a trick to remembering it. This trick could be wordplay, a rhyme, or some other little hint to help you remember.

Write the conjugations of all forms (preterite, imperfect, subjunctive, past, present, etc.) of a new verb.

Make sure you keep track of all the previous words you've learned. If you forget them it'll be harder to understand even simple sentences.

Work all year to build your vocabulary for the second language exam. Especially in the topic areas you study - 55% of your IB grade relies on the ability to use this vocabulary on your own (all of internal assessment, and Paper 2). The earlier you prepare this, and the deeper you prepare this, the better.