Other than researching Ogres as they relate to Orcs, of course. For which I have another installment, a la Beowulf illustrations. They predate Lord of the Rings by a couple of years, though not Tolkien. In fact, with a publication date of 1908, I almost wonder if Tolkien read this particular edition.
Fangs instead of tusks, but fearsome and very Uruk-hai in style, all the same. Even if Tolkien wasn't influenced by this depiction, it seems to capture the essence of the beast. I'm not sure I subscribe to Grendel as an Ogre, myself. I've always thought of him as more dragon-like, but since he's not all that well-described (and I am known for ignoring description anyway) it could just as easily be a me thing, than anything grounded in fact or literature.
But look also at the image of Grendel's mother in the same book. Green skin, blue-black hair, a long ugly nose. If anything, she's even more orc-like than Grendel, complete with rippling muscles.
We know that Tolkien was studying Beowulf -- and in fact he was one of the first to study it seriously for more than just the evolution of language. Looking at images like this, I can't imagine how the ogre isn't the father of the Orc -- or at the very least, the father of our perceptions of what makes an Orc. It's obvious that as a culture, we were already imagining them in 1908.