Coherence and Cohesion
The Coherence and Cohesion criterion is exactly the same for General Training and Academic Tasks 1 and 2.
Coherence refers to the flow of your writing. That’s how your ideas are organised into paragraphs that are properly sequenced and easy to follow.
Examiners are looking for how you have organized you answer into distinct paragraphs and how your ideas are logically supported and expanded.
Cohesion refers the use of cohesive devices or linking phrases and words that connect and show the relationship between parts of sentences and paragraphs.

Click on the following link for a list of common cohesive devices.
IELTS Writing: Cohesive Devices
Be sure of the meaning of the cohesive device and how it can be used in a sentence. A reputable dictionary will give you the definition, pronunciation, examples, synonyms, collocation, related words and the CEFR level.
I recommend…
the Cambridge online dictionary.
https://dictionary.cambridge.org/us/dictionary/
Once you are certain of the meaning and how to use them, practice using them when answering the question. Learning lists of isolated cohesive devices is not a useful strategy unless you are sure about the meaning and how they are used in sentences.
Although band 7 says “uses a range of cohesive devices” it’s not necessary to use several in each sentence. Candidates often spend a lot of time memorizing lists of cohesive devices but you don’t need to remember 6 or 7 of them on how to give an example when 2 or 3 is sufficient range.
Most candidates use cohesive devices at the beginning of a sentence. However, you should use these within sentences.

Example:
However, the disadvantages should not be ignored.
The disadvantages, however, should not be ignored.
Also included in the Coherence and Cohesion criterion is referencing and substitution.
Referencing is using pronouns (it, they, them, this, these… etc.) to avoid repeating what you mentioned earlier. Compare examples A & B…
A: When I first tried the speakers, the speaker’s sound quality was very poor. The sound quality had too much treble.
OR
B: When I first tried the speakers, their sound quality was very poor. It had too much treble.
Example B is more cohesive in terms of referencing because it uses pronouns rather repeat words mentioned earlier.
Substitution is using synonyms and paraphrase to avoid repeating what you mentioned earlier. Compare examples A & B…
A: Soccer players, in my opinion, earn way too much money. I believe that salaries for all footballers should be capped.
OR
B: Soccer players, in my opinion, earn way too much money. I believe that salaries for all soccer players should be capped.
Example A is more cohesive in terms of substitution as it doesn’t repeat a word mentioned earlier.
Clear and appropriate referencing and substitution is necessary to move above band 6 for Coherence and Cohesion.
