Speaking only for myself: Have friends who are native speakers and interested in the same subject and compare notes. Pulp studies tends to be a small pond (well, a couple of puddles connected by streams), so usually if you get involved in a particular community (Lovecraft studies, Robert E. Howard studies, Edgar Rice Burroughs studies, etc.) you identify the big names and keep tabs on their work and they keep tabs on yours; social media like Facebook and email makes that a lot easier than it used to be - Lovecraft in particular had some early adherents in France and Germany who produced some interesting work, but most of it isn't available in English, and even getting an idea of what's out there at any given time is difficult since the bibliographies are always out of date - but if you have a local that's in the scene, you can get an idea of what's going on, and maybe trade things.

Many of the major journals that cover early medieval topics are international and take articles in English, German, Italian, and French, and the articles cite recent books in those languages too. Knowledge of each of these (and Latin) is pretty standard among early medievalists, so if scholars writing in Italian, for example, are at the forefront in one particular area, their work is still accessible to others working in the same area. (Many conferences are also international, so that you can meet people from around Europe working in the same areas.)

I'm subscribed to newsletters from Italian, UK, and US institutions. I also get spammed by professors hawking their latest books and articles on both sides of the pond. It's all about being on the right mailing lists ;-)

It seems like most academic journals provide at least an abstract in English these days, and that helps me out a lot, as it lets me know if it will be worth my effort to try to pick through something. I guess I just assume that I'm missing any major developments published without the English abstract, as I won't catch them on a keyword alert! :(

Also, kinda embarrassed to mention this, but Google Translate is actually really good at German in particular, and I've easily picked my way through German material before. It kinda alphabet-soups Italian and French still, the other languages I'd like to "read" material in, but the German translation for whatever reason is really good.