When designing your comic's UI, make sure you include:
- First/Previous/Next/Last buttons near the comic - Some comics don't include the first and last buttons, and others put the whole set in a place that's inconvenient to readers. Generally, it's a good idea to have the full set on the bottom and optionally the previous/next buttons on top.
- Clicking the comic goes to the NEXT page - Many comics don't have this feature, and I know of at least one (plotless) that goes backwards instead, which is annoying when you want to start at the beginning. This makes catching up to your comic convenient and will make the reader more engaged.
- A nice design - If the design of your comic's website makes the reader want to puke, they may not want to stick around to read your comic, no matter how good your plot or art may be.
- Centered Pages - It's obnoxious when a page is aligned all the way to the left or right. It grates on people's nerves and distracts them from the actual content. Please center your pages!
- Navigation - Make sure the navigation of the site, including the actual comic pages, news, links, about page, etc. are all easy to see and easy to go to. Generally you should put this on top or to the sides (be careful with this - auto-scrolling link menus can be screwed up royally on mobile systems)
- Comments - Quite a few comics don't include this. Some replace it with a forum. But, for the most part, it is VERY handy to have a comment section for every page as it gives readers easy access to give you tips, suggestions, or discuss what's going on in the comic. Forums can do that, but they're harder to get to.
- Page Access - This is more of an annoyance than anything that's really necessary, but I find it really annoying when webcomics use a system based off of dates or random hashes to name page URLs. That's stuff like comic.com/18-30-11/page-name or comic.com/742917/page-name (which SJ regrettably seems to do). If you actually care enough about this, name your URLs after the page's number, or a chapter-page combination.
There are also many comics that don't include certain pages that can be really helpful.
- A well-written about page - This should be in EVERY comic and I have no idea why it isn't. Unless there's something astounding that catches a reader's eye, they're going to want to know what the comic is even about before they start reading 300 pages of it.
- A character page - While it's acceptable to not include this for small casts, larger casts can be difficult to remember, especially when they have foreign names or the comic updates less than several times a week. This is, however, optional, and if you DO include it, make sure it's only supplemental and consistent with the actual content of your comic.
- A links page - Show some of your fellow authors some respect, and give your readers more comics for them to read. It's always a nice surprise to find a really nice comic, finish it, and realize the author reads a comic you like.
- An archives page - Who wants to frantically press the PREV button in search of that one really funny page? Archives make it easy to find specific pages readers like, and can show off your dedicated upload schedule.
- Links to your personal stuff - Websites like DeviantArt, Tumblr, and Youtube are the go-to place for readers who like your art or humor and want to see more than just your comic.
- Your update schedule - Readers want to know when you update. Please please PLEASE put your schedule somewhere obvious like on top of every page, even if it's irregular updating (you can just say "whenever" or "every few weeks")
- Avoid big banners/ads at the top - It's nice that you have an enormous header that you want people to see, but it's irritating to have to scroll down just to see the comic. At least make it small enough that we can see the first few panels.
All of this UI stuff is fine and dandy, but what about the actual content of the comic?
- Buffer - If you haven't published your comic yet, make absolutely sure you have at least 20 pages of comic buffer and 40 pages of script. This makes updates more regular and keeps you from being stressed. If you're already publishing, try as hard as you can to make maybe an extra page per update to build one.
- UPDATE OFTEN - You should have an update schedule of at least once per week, and you should ONLY do that if you're busy or the art takes too long to make more than one per week. Anything slower than twice a week makes the plot as slow as molasses and easy to forget. The best update schedule is Mon/Wed/Fri, or something similar.
- Guest Comics/Filler? - These are OK when you're on a short hiatus, but don't include one as an extra or because you couldn't make the day's page. It's jarring to be rushing through the story and see an unrelated page out of no where.
- Art - Don't think you have what it takes to draw the comic? Several comics started out with low quality and evolved into beautiful works of art after years of practice, and there are some that maintain a nice simplistic style. However, there IS a limit. If your comic requires nice, detailed art or you just can't draw, you can also consider a partnership.
- Writing - The whole evolution of art thing doesn't really apply here. Writing is something that makes or breaks a comic -- if there's a lot of plotholes, unrealistic dialogue, or long, boring series of pages to start with, new readers aren't going to stick around.
Sorry if I insulted anyone with my examples or words -- I'll take them down on request.