this is a pretty basic one most folks know, but I think the biggest thing is just how long it takes to do and how long it takes to tell if it's worth it.
Like, you could read 200 pages in an afternoon, but it's taken me 5 years to create that many. With weekly updates (the fastest I can manage) a single chapter takes an entire year to get through. And you have to decide how you want to respond to that huge pacing problem; you can focus on the update readers and write your story to be paced quickly enough that something new happens on every new page, that it's designed to be read one-page-a-week and still feel satisfying, OR you can focus on the archive readers, using atmospheric pacing where a page might just be an establishing shot, knowing it will make your comic very slow for the regular readers but it'll work well when it's finally collected as a book. Neither one is right or wrong, but it's a question you have to answer for yourself when you're deciding how to present your story!
And for the second thing isn't really an art practice, but it's kinda... super vital perspective. When I was just getting started, I got the advice: "Do your webcomic for about 2 years before you make up your mind; that's the point where you can really tell if you're enjoying it and if it's worth it to you, or if it's too much trouble for too little reward." In my experience, it's good advice -- it's gonna take at LEAST a year to start finding your audience. Folks will often update for 6 months and then wonder why they only have a small number of readers, not realising that this is the norm. I was 50 pages into my first comic before I started getting 1 or 2 comments that weren't like, from my IRL friends. Of course it's fine and good to be invested in building a readership, but you also really, really have to love it even when you know it's gonna take years before you see anything for your efforts.
It's sorta like planting a fruit tree. It's gonna take the tree years to grow, and you don't even know if the fruit is gonna be good when it finally comes. You kinda have to enjoy the process of growing a tree, at least a little bit, or it's gonna be a frustrating experience. And you have to go into it knowing that you won't see fruit for a long time, and still believe it's worth it.