How do you decide when you have enough research results to write a paper and to which journal you submit the paper In some research area in CS we got some very interesting results. Now we are thinking about publishing them. In the group we are, the philosophy is to publish inmediately small things in conference papers, which is ok but not the best. Now I am thinking about collecting more of these "small things" and publish in a JCR paper, impact factor more than 2. My question here is how would you decide when you have enough material to prepare a decent paper in a JCR journal? And furthermore, once you think this is ok, how would you decide to which journal you submit the paper to?

PS: JCR refers to Journal Citation Reports, an extensive list that collects info about the most representative and relevant journals in all scientific areas along with their impact factors, so they are usually refereed and no conference papers there
JCR is part of the ISI Science Citation Index family of databases, which is not especially reliable in its measurement of computer science impact. See for instance this report from Informatics Europe which specifically warns against using ISI databases to measure the impact of computer scientists.

In any case, if you want your papers to get attention from other computer scientists, publication in selective conferences is still the way to go. We can argue whether it should be, but that's what it is. Some conferences (e.g. SIGGRAPH) count as a journal directly (their proceedings are published as a special issue of a journal), others (e.g. FOCS/STOC/SODA) expect their authors to later turn the same material into an expanded and more polished journal paper, but the conference is to a large extent how to signal other researchers that your work is worth paying attention to. If you're not familiar with the conferences in the area, choosing one sponsored by ACM or IEEE over one that isn't is a good rule of thumb, as is choosing one that calls itself a "symposium" over one that calls itself a "workshop".

However, that doesn't mean that you have to partition your work into least publishable units as you describe your coworkers doing, and it also doesn't mean that saving up multiple small results into a single paper is a good way of making your papers stronger. It's certainly possible to publish papers like that but to my mind the better ones are often the ones that have a single strong main result, perhaps with additional results on the side not to strengthen the paper but rather to provide more complete coverage of its subject.