There are a number of elements that factor into sequential storytelling: page design, background, lighting, staging, and a handful of others — but the one I find myself leaning on the most to carry across a narrative is my characters’ acting, and by extension character interaction.
Not to assume at any theatrical skill on my part, but I like to think I’ve seen enough movies and TV shows (good and bad) to know how effective acting can be a powerful storytelling tool. I’ve broken it down into sub-facets to help illustrate the point:
Expression covers not only facial distortion but also speech delivery. The wrong look can make a bit of dialogue ambiguous, which is one of the worst things in a visual medium. It is worth learning that anger isn’t merely a furrowed brow and that surprise isn’t simply bulging eyes. It is equally worthwhile to remember that someone yelling doesn’t always bear teeth and that someone smiling is not necessarily squinting as well. Think about the dialogue being delivered (if you have a full script), and more often than not the right expression for your character will present itself to you. This is where observing the nuanced performances of the likes of Gary Oldman and Meryl Streep pay off.
Body Language and Gesture come into play when wide angle shots or limited panel space leave facial features too distant to make out. With the right physical presence, any character is able to deliver thought and intent without ever having to say a word. Some masters of silent sequentials are Stuart Immonen, Frank Quitely, and Dave Gibbons.
Props are of use when a character not only interacts with another, but also with his environment. Different people will have different ways of holding their glasses, just as one man may angrily rip a phonebook in half in a burst of rage while another will tear the pages out one by one as his anger builds. In this sense, it helps to know the kind of character you are portraying so that you can vicariously perform the action for him. Some films I would recommend for prop use are Ocean’s Eleven, Scent of a Woman, and The Usual Suspects.