Does presenting results in conference and publishing in unreviewed proceedings prevent better publications? Recently I have been attending a couple of conferences/workshops, presenting my latest results in oral and poster sessions. I really enjoyed doing that and the following live discussions. 

However the proceedings of these conferences are not reviewed and for many people they do not count as "real" publications. I wouldn't like to stop going to conferences, discussing with people and collecting the visibility that arises from this, but on the other hand I also wouldn't like to waste my precious results in publications that are not seen as serious enough.

What is the best practice in this case?

I spoke with people saying that they do not even bother about writing workshop proceedings, but I don't feel quite comfortable with this approach.

My field is accelerator physics, especially machine design and beam dynamics simulations.
While I do not know accelerator physics in particular, for most fields and most journals, a non-reviewed publication does not count as prior publication.  If this is the case for accelerator physics as well, then putting an extended abstract in a non-reviewed conference will not block you from publishing an improved full paper in a journal later.  The prior version should be explicitly acknowledged in the journal submission.

The other reason that you might end up with less publications is internal rather than external: once you've put it out and gotten your feedback, you might not feel as strong an urge to do a formal peer-reviewed publication.  If this is the case, then you need to ask yourself whether this is actually a problem for you or not.  I, for example, have a number of publications that have never gone beyond technical reports or white-papers, but am comfortable with that because I think most of them did not need to have a full publication, and I've got enough others.  If you are a person who has difficulty motivating yourself to writing up results for peer review, however, you may want to consider the spur to publication as valuable and therefore avoid the non-peer-reviewed pre-publications.