How to improve student seminar presentations and seminar papers During the last semester my supervisor Prof. X held a seminar for bachelor and master students (mostly computer scientists). According to the study regulations the students have to 


give scientific presentations (based on journal or conference papers) and
hand in seminar papers on the topic of their presentation (i.e. their papers should cover the results of the original paper, lay out details of proofs, add additional explanations or examples, etc.).


The final grade consists of 2/3*presentation + 1/3*paper.

Prologue. 
At the beginning of the semester Prof. X's research assistants compiled a list of interesting research papers. At the first seminar meeting the students were able to choose the paper they would like to present to the rest of the group at the end of the semester. Furthermore Prof. X made it very clear that understanding the topic is just a portion of presenting and writing down scientific ideas. Every student was assigned to a seminar supervisor to whom they could talk when they ran into problems.
Half-way through the semester there was an obligatory meeting with the supervisor and a deadline for handing in a draft of the presentation slides. At the end of the semester we organized a little "conference" and the students presented "their" papers. Afterwards, they received written feedback on their presentations from all participants (students, research assistents, and Prof. X). Six weeks later they had to hand in their seminar papers. 

Problem.
Unfortunately the quality of many seminar papers is relatively poor; even the papers handed in by students who had understood their topic "quite well" and had given good presentations are surprisingly different from what we expected. 

Main issues:


Even though they were allowed to use their native language, many papers had bad spelling (obviously no spell checker was used) and bad grammar.
In some cases it was impossible to understand the basic ideas if one had not already been familiar with the subject. 
Imprecise language and almost no sources cited, e.g. "Algorithm Y is rather efficient in comparison with other algorithms." [citation needed].
Some students only cited a single source (= "their" research paper).


Questions. 
How should we address these issues? Of course, we are going to give some feedback on their seminar papers. I am worried about the next seminar. Reading all these papers was (mentally) exhausting. Should we require that seminar papers must be handed in first? How could we install an iterative feedback process?

I am looking forward to your ideas and experiences.
This sounds exactly like the situation we are experiencing at our university as well. We have improved the situation by forcing the students to write papers and similar texts every semester (starting from semester 1), in different settings, and we're giving detailed feedback afterwards. In our first and second semesters we are using this setting for one course:


Students can select one topic and prepare it in a group of three (the idea is to mix people so they can give feedback within their group). We emphasize that everyone will receive a grade based on personal efforts and success, and there is no group bonus / malus. 
They will present the topic in a group of three (20 min presentation + 10 min discussion) 
We are giving a 3h presentation on scientific writing.
They have to give their paper outline to their supervisor after about 3 weeks. The quality of feedback depends on the effort put into the structure. If they hand in "Introduction, Main Section, Conclusion", they will receive a "correct, but good luck" ;-). 
They shall hand in a first version after about 50% of the course. This version will be discussed in a personal feedback session of one hour by a scientific journalist
At ~3/4, they have to submit their "pre-final" version to a conference management system. 
Everyone is now switching roles and becomes a reviewer. Every reviewer has to review two papers. The quality of reviews is part of the final grade.
After the reviews. the groups have one more week to finish the final paper submission.


As said, we are following this highly intensive approach in semesters 1 &amp; 2. In the subsequent semesters, we are having other settings, but we force them to write every semester. It seems to bear some fruits since the quality improves over time, but it's clear that we can't fully repair what went wrong during school...