1 Focus on the words you do know and try to guess what the question might be asking - IELTS always talks about typical controversial subjects, subjects that you have probably thought about/ spoken about or heard about. SO, put together the words you do know and make an educated guess.
2 Decide if it is really important to try to understand the unknown word or not - it might be completely irrelevant so do not waste your time on this.
3 Use your grammatical knowledge to guess the type of word E.g. verb, noun, adjective, adverb.
4 Use your lexical knowledge to guess the meaning of the words. E.g. break the word down, think if you know any words that look similar.
5 Look at the other words around the unknown word to make a guess.
The most important point here is to stay calm. You will never understand every word in the IELTS so you need to accept that you will probably face this situation of not knowing some of the words in the title - this does not mean that you cannot answer it. Remember to use all your knowledge and your common sense to make a guess - the title does not usually talk about strange topics that you have never heard of before - it is common issues that are often discussed. So, think around the words you do know and make an educated guess.
Vocabulary:
extremely (adv) = very, very
typical (adj) = common, usual
controversial (adj) = people argue about this
irrelevant (adj) = not important, not connected
lexical (adj) = related to vocabulary