If you've been a reader of Webcomics.com or a listener of ComicLab, you know how much I loathe "magic number" advice. But as much as I detest typing it, this "one weird trick" will almost certainly improve your comic.
Collect your thirty most recent comics (strips or pages... it doesn't matter) and get ready to read them, one by one. Now, instead of reading them from the beginning, start reading each from the second panel. If you're like most amateur and pro-am comics creators, your comics probably read perfectly fine this way. And that's a Big Problem.
This is a common stumbling block. In fact, when I teach my Storytelling class at the University of the Arts, I see my writing students doing the same thing. Their best opening lines are often found in the middle of their first paragraphs!
It happens so often in my own work that I habitually cross out the first panel of nearly every sequential comic I write before I even consider drawing it. More often than not, it's an improvement!
If your first panel is extraneous, your comic will be boring. It will feel slow and plodding instead of being a brisk, engaging experience. If you're trying to write humor, this is a death sentence. Humor thrives in precise timing. If you're wasting time with needless panels, your punchline is suffering. Moreover, if you excise an unnecessary opening panel, you can use that extra panel to improve the joke's setup. Humor relies on an internal tension-and-release mechanism. Improving that tension will increase the comic's humor potential significantly.