My Top 10 Tips for GCSE English Re-Sitters

I'll not waffle but just crack on with it, this SHOULD be short and sweet.

1. For them, YOU represent all that has gone wrong for these students before in GCSE English. It is not YOUR fault, but expect a wave of resentment and apathy coming in your direction. It isn't really aimed at you, you are just a painful reminder of what went wrong before. If that doesn't happen - EXCELLENT. Enjoy it!
2. Because of what went wrong before, you have a room full of mainly fragile egos. Some might appear arrogant, this is more than likely a front. Walking in and barking orders like the Stazi will do you no favours, but firm and fair management of them will. 
3. Some WILL be more able than the prior grade indicates. Things go pear shaped for students for many, many, many reasons. Sew them the idea of the possibility of doing even better than a C. The C is definitely what they need, but if they can do better, you need to let them know that they can. Keep drip feeding the idea, they'll take the hint eventually. 
4. This is a no-brainer really, but, your students are likely to have weak literacy skills. Poor sentence construction; inability to punctuate those sentences, a limited and weak range of vocabulary; lack of literary and non-literary writing techniques; unable to paragraph, and a very limited range of conjunctions in their writing. Each lesson must involve some explicit grammar teaching, but do it in baby steps. 
5. Homework - my adult evening group aside - getting homework from such classes is VERY difficult. My suggestion is to provide grammar worksheets, then within the next lesson, set a task that links to the homework, giving the students the opportunity to apply their grammar skills in the lesson. Take this work in to mark then you can easily find out who did the homework or not.  Also, by marking the work, your relationship with the students grows. It is VERY important you mark honestly, but positively. They REALLY need to know what they CAN do, whilst letting them know what they need to do to get better. 
6. If you want students to focus on a particular technique or skill in their writing, attach a points system to it. E.g. adjective - 1 point, personification - 4 points, and congeries (yup, done that with my re-sitters) 6 points - according to level of difficulty. It should also prevent a 'death by adjective listing' form of creative writing. Get students to self-mark or peer mark before you even clap eyes on it; it will get them into the habit of checking their own work, and reading it carefully. 
7. Going back to that lovely rhetorical term 'congeries' - rhetorical figures is something I have been doing a lot of with my A-Level classes. One lesson, while looking at the description of 'Dr. Roylott' from Conan-Doyle's "The Speckled Band", I reasoned, why the hell-not expose them to it? So I did. We looked at the definition, how it looks on the page, what it DOES, and how such long sentences are constructed and why. Using the points system, pupils were keen to try it. Some of them succeeded. I also told them it came from my A-Level lessons, making sure I told them that if I didn't think they were capable, I wouldn't bother. So, going back to those fragile egos, that's them starting to wag their tales right there. 
8. Another no-brainer. Turn up. Always, turn-up. This will be, eventually, rewarded with their loyalty. 
9. Have a sense of humour, by GOD you'll need it, along with this, be relentlessly nice, even in the face of their apathy and truculence. You will wear them down, because when you are relentlessly nice, they find less and less reason to be truculent and unpleasant. If they were to continue being mean, it would be like kicking a puppy. 
10. Be patient. Very, very patient. They will come round to you once they have got used to you, and learned to trust you. Like skittles in a bowling alley, it is won't be a strike, but one or two skittles at a time. Eventually, the bowling ball that is YOU and your teaching, will knock them over. (Dodgy metaphor now over).