People are always discussing ways to grow readership, but they it always seems to be speculation. I thought it might be helpful for all you to summarize some of the stuff I've tried. Even though each person's comic is unique (what works for one strip might not work for another one), hopefully you can take away some things that might help your own comic.
During the time I've been doing Calamities of Nature, I've tried a LOT of things to get people to visit my site. After over three years of consistent updating, I now regularly have 4,000-5,000 people viewing my site and 4000 RSS readers (with around 2000 checking each update), which earns me some nice extra money. I don't think my comic especially good, so I credit this readership mostly to three main things (1) consistent updates, (2) consistent marketing, and (3) lucky breaks. I don't think it's out of the question that others can generate a similar readership in the same sort of timespan.
- I have only missed 2 updates since September 1, 2008 when I first started updating 3 times per week. From January 1, 2008 to September 1, 2008 (when I updated twice per week), I never missed an update. This is important for keeping readers. I have very little sympathy for people who complain about their small readerships but can't go a month without missing an update.
- I've twice done guest comic strips for the website FMyLife.com. Each time this sent about 5,000 new people to my site.
- I have share buttons on my site to help inspire my readers to spread the word.
- During the year 2009, I took every dollar I made from advertising on my site and put it into Project Wonderful ads. This amounted to about $5-10 per day for an entire year. I've tried advertising with other services, but these weren't as good of a use of money.
- I've worked hard to optimize the amount of money I make from the site. Now this makes me some nice money, but originally this was for readership building. You see, I have a very tight budget, but by optimizing ads, it gives me money that I can spend on Project Wonderful ads (see line above). Read more here http://www.calamitiesofnature.com/extras/adservicereview.php
- I was featured on the blog Bad Astronomy twice, which sent about 20,000 people to my site.
- I've asked my readers to use the "like" button in Google reader. When you get enough likes, you can get a tidal wave of new readers, which has happened a few times, each time gaining me a few hundred new RSS feed readers.
- Each day I get around 1,000 hits from the social networking site Stumbleupon. It seems like my single gags work well with this audience, although you can argue whether this represents true readers. Either way, this traffic increases ad revenue, which I can then invest into more focused ads.
- In October of 2008, I had a table at the Alternative Press Expo in San Francisco. I passed out about 400 free flyers.
- My comic was featured on Jeff Smith's site because I made a blog post about meeting him at the Alternative Press Expo.
- The last two years I've done a guest strip contest on my site which seems to gain a lot of publicity. Also, when the winners are featured on my site, they usually link to me on their own respective sites, so it's a win-win for me. I also feature all the runner-ups in my blog for the same reason.
- The last two years I've done a caption contest. Not only does the contest gain publicity, but I have a vote for the final winner. This means the 10 finalists ask their friends and families to check out my site to vote, gaining me more potential readers.
- I was a Weblog Awards finalist in 2009 (along with Dilbert and xkcd), which gained me a lot of eyeballs.
- Since January 2009, I've been syndicated by MCT Campus to college newspapers.
- I have tutorials on my site on: coloring comics, using print-on-demand-services, and putting ads on a site. These tutorial get a lot of hits from forums and search engines. Many people know me better from these tutorials than my comics!
- I did guest strips for the webcomics Imagine This and Cowbirds in Love.
- I've had guest strips done from a number of creators who were nice enough to link to my site. This has included Michael Firman (Moe), Zach Weiner (SMBC), Audra Furuichi (Nemu-Nemu) and Jeff Schuetze (Jeffbot).
- My comics have been featured in a number of atheist and science forums.
- My comics have also been featured on a number of atheist and science blogs.
- I ran a contest on my site to transcribe all the comics, with the a random winner getting a $50 gift certificate. Surprisingly, a lot of people seemed to become very invested in the comic from this experience.
- Each fall I ask my readers to post flyers around their comic and university campuses. I only get minimal feedback from this, so I'm not sure how effective it is.
- I've printed postcards from Vistaprint (which often has really cheap deals where you basically only have to pay for shipping) and them left them as freebies at local coffee shops. (Although I must admit I'm not sure how many readers I've gained from this.)
- I concentrate my forum and blog reading time posting in forums and blogs with themes that match my comic. This has a much better chance of gaining me new readers in comparison to posting in webcomic forums. Plus, it gives me more ideas for writing new comics!
- I used to post my comics regularly to the website http://www.toonsup.com/
I even got a monetary prize one year for having the 3rd best rated posts (which was cool since my comics are in English and it's largely a German site)
- I use su.pr when posting my comics to Twitter, which helps me track the hits and increases the change of my comics getting stumbled
- I have a Facebook page for my comic which automatically updates from my RSS feed. Many readers share and visit from this page. It's almost like a forum that people don't have to sign up for. I also try to post interesting links that fit the themes covered in my comic and start discussions http://www.facebook.com/calamitiesofnature
- I had a comic featured on the front page of Digg twice, gaining me about 100,000 new people to my site in each time. Although I don't any of them have stayed around, it did gain me some opportunities to publish comics in magazines.
- Last fall I took comments off my site, drawing lots of angry emails-- oh wait, that probably actually lost me readers!
I've probably forgot some things, but hopefully that gives you some idea of the things I've tried to do promotion. The sad fact is that unless you're a superstar (and I'm not), you need to promote almost as much as you draw if you want to gain an audience. And the even sadder fact is that the best traffic (traffic that actually sticks around) has been when my comic has been featured on blogs, and this is something that's basically completely out of my hands.
Even though webcomics are free, there's only so much time in a day. Most people probably read 5 to 20 webcomics per day, so if you want them to become a regular reader, your comic better be better than one of the 20 other webcomics that person reads. Not an easy feat! There are some good webcomics out there. It's even harder if you want people to actually buy from you.
One thing to keep in mind is that even harder than getting readers is KEEPING readers. If you spend enough money on PW, you can get thousands of people going to your site. But if they don't like what they see, they're not coming back, and they're definitely not telling their friends. I wonder many times whether my comic has enough appeal or whether, given all the promotion I've done, I should actually have a much bigger audience if I just did a better comic.
Hope this is helpful! I've had this sitting on my computer for a while, because I wasn't sure how useful it would be for everyone. I'd be interested in hearing if other people have helpful info to add.