I only teach A level, so I don't know if my answers are relevant to you. However, we have just done our quality circles and got quite good feedback on the marking we do.
All students have their essays marked, and a top sheet is used. The top sheet basically breaks down the requirements of the grade descriptors into the constituent parts (use of key terms, knowledge of scholars, understanding of key concepts etc) and for each criterion, the sheet is highlighted to see whether they are at level 2/3/4 on the mark scheme.
At the end of each assessment objective (there are 2) there is space for comments. I usually comment on something that has been done well, and something that they could improve on (this received good feedback in our QC).
Then at the end of the sheet, there is space for a few targets to be set. This is something that I want them to work on for next time, like to include more key terms etc.
Throughout the essay, I will also annotate. I tick furiously at very relevant point, so a good essay is full of ticks, whereas if they waste time on background info, it will be a passage that is blank of ticks, because there's nothing of value there. The students quickly learn to see where all the ticks are congregated. If they do write wrong passages (eg put Ao2 in Ao1), then I do cross through their work and explain why in the margin.
When we give back the essays, we do try to briefly talk through their essays with them. The students often say they would like more verbal feedback, but it is hard to fit this in, because to talk to very student individually essentially costs us a lesson.
Oh, and I do have a sticker system, which bizarrely the students really like. When my colleague introduced it, I laughed and said the students wouldn't want gold stars, (as they're all over 16), but bizarrely we have had really good feedback from it, and they get really excited about stickers, so now there's a whole range of them from smiley faces, coloured stars, gold stars and for amazing work they get a special "Lecherrs thinks this is excellent" sticker. We've had stickers a few years now, but it still makes me laugh when I see 18 year olds getting excited over the fact they have got. Sticker!
And the last thing, I am very clear with the students that essays are all part of the learning curve. Nothing counts until they sit the exam in May, so they should use their essays to try out stuff, make mistakes, and improve. I mark from the mark scheme from day 1, and some students do find that hard, as they start off getting Es (and that's with having their first essays scaffolded for them), but I am very clear, that over the year they haven't just got to learn the subject, they have also got to learn how to write an AS essay too. It's all part of the learning curve. Some students (particularly A grade GCSE students) can struggle with this, even though I constantly reassure them that it's all part of the learning process, and nothing counts until may. Over the course the year, they will write 10 essays for me and my colleague (one for each topic they study) and then they do 2 mock exams. All essays are written in class in timed conditions (with help at the start of the year).