It's hard to tell you what not to do, partly because there's a lot you shouldn't do, but also because a lot of things that might seem awful can be done very well. I recommend hopping on TVTropes and familiarising yourself with some of the tropes you expect to have in your comic (warning: TVTropes will suck away all of your free time if you're not careful). I recommend looking up works that are somewhat similar, and looking through their trope lists. See which tropes work well for those works and try to figure out why that is. Same for tropes which work against them. But remember:
Tropes are not bad!
You could post your story summary and character concepts for critique, so that we can give more concrete pointers.
Also, do
not set out to make a comic everybody will like. You'll only set yourself up for disappointment. Make a comic
you would want to read, and try not to turn away everybody else in the process.
Catchy titles: There's no "how to" really, it's a matter of trial and error.
Some criteria that might help:
1. Keep it easy to remember/say/spell. Most people take this to mean "make it short", but it doesn't have to be. "Lord of the Rings" isn't all that short, and neither is "A Series of Unfortunate Events", but these are successful titles because they're simple to remember and they don't sound like other things. They're composed of words everybody knows, but in contexts that aren't very typical, which makes them memorable.
If you want to be daring and use fictional words/names as your title (e.g. Skyrim, The Hobbit, Ayreon), you should make them easy to pronounce and make the pronunciation evident from the spelling (note that this depends on the language of the audience, so base it on your target audience).
2. The title should give the feel of the work. Tone and theme are the big ones here. A fantasy work would benefit from having fantastical concepts implied in the title. Hinting at the setting is good too, but explicitly stating it is usually a bad idea since settings are usually
not the main draw of a story.
So, "The Dark Tower" (hinting at a bleak tone and some sort of important, fantastical tower - a non-fantastical tower probably wouldn't be "dark"
) is a better title than "The Gunslinger" even though both are relevant to the story - the latter says nothing about the tone, and gunslingers are associated with westerns and specifically crime-themed action stories.
3. Avoid being overly specific. The title is one of the first opportunities you have to grab potential readers. At that point, they don't
care about anything in your story, so if you throw something at them that only has significance to someone who has read the story, it's not going to stick. You can certainly reference story-specific events and concepts in your title, but they should sound intriguing on their own. Most readers aren't going to care about "Blake's Frog" unless they already know who Blake is and why a frog is significant at all, but "The Mage's Frog" is a bit more interesting because it gives some more general context, and provides an unusual juxtaposition.
4. Avoid being overly general or describing the entire genre. This one is closely related to #2. The title should be specific to the work, and should probably not work well for any other work. A generic title doesn't make people interested in
your work, and it makes it sound like your work doesn't bring anything new to the table. "The Witch of New York" sounds like a generic urban fantasy set in NYC, or worse - like an essay about either history or the genre. "A Summoner on Broadway" sounds much more specific and even implies what some of the stakes in the story are - Broadway is famous for its big theatres, so if something nasty gets summoned there, a lot of people would be in danger. And that's fun to read about!