Often, as soon as I submit a pre-submission paper on the arxiv, I receive a couple of emails from other researchers pointing out their previous relevant work, which in their words is connected with mine and deserve citations.
Sometimes, it happens that their work is really connected with my work, and perhaps even anticipating it. For some reason I was not aware of that, my fault. In this cases, I usually add the citation and even refer to the work in a more extensive way.
However, most of the emails just point to works that are indeed on the same topic, perhaps also very important works in the field, but which are not even similar nor related to my work. In this cases, I really don't know what to do. I could inflate the reference of the paper, giving credits to papers which really did not contribute in any way to my work. Or I could just ignore it, with the hope that one of the authors of that papers will not end up to be one of my referees...
What is the common practice in this cases?
(see also this question for another point of view)