To help students with the organisation and relevance of the piece of writing, students can pass their piece of work to others in the class. The students then act as critics or editors and give their opinion on the written work. There isn't one correct way to organise a piece of writing and everybody will have something useful to say. If you are able to work in a computer room, then students can swap computers to review each other's work.
You can also incorporate a reading activity in the middle of the writing process. After you have finished the reading, the students might have new ideas for their writing and can go back to reviewing their own work. If you choose to do this, don't use a text that is radically different to the organisation they are using as this might lead to confusion.
When students are focusing on accuracy, the task can feel daunting and overwhelming. You could tell students that during the first review, the focus is on tenses. They then look out for mistakes only in verb tenses. They can then do a second review, looking at prepositions, for a third review they can look at punctuation and so on. This has the added advantage of helping them to be more focused in their reviewing and so more errors can be detected.
You could also review their work, but rather than correcting it yourself, indicate that an error exists. Depending on the level and whether you feel the students can handle it, you can underline the word that is incorrect, you can indicate that there is an error in tense usage or simply indicate that a sentence contains an error and leave the student to find it for him or herself.
It is important to remember not to overdo writing activities. You can spread out the work over a number of lessons and set some of it for homework. It is even advisable to do so.
I hope you will find this useful.