Aha!!!!, somebody called an advertising student???
(sorry, got excited)
There are many tricks to do that.
I will asume we don`t have money to advertise in this scenario in case budget is a problem.
Before advertising/marketing make sure your content can give a good first impression.
1-Viral Marketing: to get people to talk about your comic and share it. Which kind of viralization works depends of your content. For example, "Leaking" some fake spoiler about your comic on social media, or an image that calls atention without context may cause people to share it.
2-As KoreanTacos said, encouraging viewers to share your comic can work wonders. If they love your work they will not have problem sharing it, and the credibility of a friend/ family/ a person you trust is stronger than any ad.
3-Memes: well, you cant force memes, but you can encourage them with your content. For example, a memorable quote, memorable scene, an epic facial/body expression can do wonders. Even a scene that break people`s hearts can become iconic. As long as it is memorable.
I admit i am trying to make my comic as memorable as possible with this as one of the reasons. How well/bad this works the future will tell. Even in the scenario it doesnt work, this will be usefull to help me write better.
4-And of course you have forum marketing:
Share your comic in apropiate topics. For example, one about describing your OC`s. If you have good knowledge about an aspect of making comics, like art, composition, writing, characterization, etc.. you can give feedback when it comes to the aspects you know well.
At least two of my readers got interested in reading my comic for the feedback/opinion i shared.
Also, the description. Choose your words so your comic wakes the curiosity and interest of people, but your description must tell the truth.
Hope this helps!