Task 2 responses are assessed on:
Task Response,Coherence and Cohesion,Lexical Resource,Grammatical Range and Accuracy.
Most students/teachers focus on vocabulary and grammar so they will not score high bands in writing. IELTS writing need 4 competencies as above mentioned and all of those are equally weighed. So don’t try to focus overly just on grammar and vocabulary but think about coherency/cohesions and task response/relevancy. How?
Task response/relevancy :
This criterion assesses how appropriately, accurately and relevantly the response fulfils the requirements set out in the task, using the minimum of 150 words. General Training Writing Task 1 is a writing task with a largely predictable output in that each task sets out the context and purpose of the letter and the functions the candidate should cover in order to achieve this purpose.
Required skill for Task response: analyse the question word by word not by sentence or sub topic/main topic wise.Remember your 25 words of e*ssay topic is the one going to be more 250 words.So you should equally focus on your e*ssay topic and expand it appropriately ( equal distribution).
Coherency = explain the reason clearly and develop sequences logically.*This criterion is concerned with the overall clarity and fluency of the message: how the response organises and links information, ideas and language. Coherence refers to the linking of ideas through logical sequencing*.
Just Use one point (only) in each paragraph( to avoid confusion).Each ideas should be supported with sub-ideas with linkers.A good paragraph can answer 4 questions such as WHAT,WHY,HOW and EXAMPLE.
Example:
what? what is the point you want to state( I disagree with public smoking)
Why? just write a valid reason in few words but no more than a sentence.(smoking related health issues)
How? Explain clearly and develop/expand the REASON/WHY part.(public smoking–>nicotine–>exposure+ environment–>inhale+others–>lungs–>blood–>deposited or so on .Explain the phases clearly how public smoking causes health issues.So develop clearly and logically)
RELEVANT EXAMPLE: just don’t use any example but relevant.
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The Coherence part can be done several ways but logical sequence  is very crucial.I have done a rough example there for you but it is only a possible approach.Therefore,Clarity is the main key .Coherence is more elusive but it has a lot to do with the way that the propositional content of texts is organised. If the content of a (written) text is organised in such a way that it fulfills the reader’s expectations, it is more likely to achieve its communicative effect. This means that learners can be helped to write coherent texts through the analysis of the generic features of particular text types. This has long been the approach to teaching business, technical, and academic writing.  More important still, is second-guessing the intended reader’s questions, and then answering them. This means that it is important that, when doing writing tasks, students have a clear idea both of the purpose of the text, and of the intended readership. Good writers are able to “keep their reader in mind”. Keeping your reader in mind does not guarantee coherence, but it would seem to be a prerequisite. Â
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COHESION:
To combine logical sequence in an order ,use COHESIONS/LINKERS
Google linkers/cohesions or pleas check this out for more info —–>(http://www.onestopenglish.com/support/ask-the-experts/methodology-questions/methodology-coherence-and-cohesion/154867.article)
https://www.teachers.cambridgeesol.org/ts/exams/academicenglish/ielts/academicwriting?tab=marked <—- Academic writing
https://www.teachers.cambridgeesol.org/ts/exams/academicenglish/ielts/generaltrainingwriting?tab=marked <—–General writing
