How do you judge the quality of a journal?

The way I usually choose journals is by looking at where people I trust/follow publish, and where previous work was published. It is usually not too hard to compare the quality your work to the quality of the work you are citing, and chose a target based on that. Unless your field is highly mutli-disciplinary, you will see the same journals/conferences popping up again and again in your references; submit to one of those.

Before submitting, however, it is always important to look at a few articles from previous issues. This will give you a second gauge of quality for the journal and also let you pick up on any formatting and presentations quirks that might be present in the publication.

You may want to check that the publisher is not on Beall's List of Predatory, Open-Access Publishers.

Surprisingly, the publisher in question is not. I've found Beall's list to be fairly comprehensive, but the vanity press industry seems to be booming.

Caveat: that list is just one guy's opinion. But it resonates with my own experience.

Update: As of late January 2017, Beall's list has been taken down.

The best way is by word-of-mouth: ask around the department, ask your PhD advisor, ask people you've worked with.

If it is a specialist journal, and you are a specialist, then the next best way is to look at the previously published issues of the journal and see what kinds of articles they accept.

Failing that, the Australian Government's Research Council puts out a ranking of journals and conferences every now and then. It is not perfect, but should give a rough idea of where a journal places in the eyes of the bureaucrats :-). Note that "new" journals (journals that have not been active for more than X years) are not ranked, so omission from the list does not necessarily mean that the journal itself is not worthwhile.