What are some good things to make explicit between a student and his supervisor when beginning a PhD? This question is motivated by the fact that my last research internship was unsatisfactory in my relation with my supervisor. Partly because of me, I may have tried to be too much autonomous, rarely coming to him or sharing what I was doing or reading and never asking feedback. We didn't produce much and by the end he shared with me his disappointment, which strangely was a bit surprising to me, I was blind to the situation and our lack of exchange.

Now, I'm about to start my PhD with a totally new supervisor, and I'd like to learn from this mistake. I'm deeply convinced that the experience will be much more fulfilling for both sides if we maintain stimulating exchanges.

I was thinking about having from the beginning a long discussion about his expectation from me on short, mid and long term, his availability and the way he would like to supervise and push me.

Is this irrelevant or too much? Have you already had similar discussions? Have you tried something else?
Having a discussion about the PhD project specifically and expectations in general is always a good idea. If there is a clear project lined up it will be useful to discuss the details, possible directions, publications etc. In some cases (systems/programs/traditions) it is useful (in fact mandatory) to write a research plan or to write a review of the field as part of reading up on it. It is necessary that both you and the advisor has the same view of what should be achieved to the extent the specific program allows.

Apart from the science it is useful to discuss expectations so that you can agree on how work should proceed. Should you meet regularly? if so how often? How much feedback should you expect? Well the questions are many but having such a discussion is useful, particularly if you can also note what you agree upon on a piece of paper. In my country, one actually signs an individual study plan that is followed up annually showing progress in terms of course work and research. having such a plan is actually constructive in that it makes it possible to see if you are on track and also identify if and when your plan needs revisions and goals may deviate from the originally proposed. But, of course, all this is something which to some extent is dictated by the traditions in the specific program.

So do take the opportunity to have a good talk about the future collaboration. you will robably sense if the discussion is received well by the advisor and adapt accordingly.