Your story should go through the usual arcs of the plot, but there are some things to keep in mind.
Have an addictive plot
This is the most important since the goal is to keep your viewers coming back. A good example is the show 24. That damn show knows exactly how to keep you coming back with its twists (sucked me in hook line and sinker). You want to keep your viewer constantly wondering.
Keep the viewer on the edge of their seat
Create highs and lows within your story. Problems must arise every so often otherwise the viewers will get bored. I like to call it “shiny ball syndrome.” Not many viewers would care to read about a group of characters continuously journeying through a forest without something disrupting that flow.
Don’t fool the viewer too many times
I’ve already stated to have continuous problems throughout your story. However, you don’t want to overuse this power otherwise it will appear too gimmicky and fake. You don’t want your viewer to realize their being led on for no particular purpose. Too much of a good thing can get boring. Also all your “problems” must make sense to your overall plot. Remember not every “problem” has to be a monster or something popping up. It could be as simple as a character having to make a crucial decision and so on (Maybe your main character loves one of the other members in their group, but they don’t know how that member feels about them).
You need to have subplots in addiction to the main plot
This gives your story variety and muscle. Every viewer is reading your Webcomic for a particular reason. Some love character dynamics, romance, action, growth, etc. Nothing is one note in life or story. No character will get along perfectly with another…need I go on?
Create something Talkworthy
This is my favorite tool. There is nothing I love more than the satisfaction of being influenced by a particular movie, show, book, etc. enough to run to a friend and spill my guts on how greatly it affected me. You can accomplish this by using all the points stated above. The most effective I feel though is through emotion. Empathy is a powerful tool when used right. Once you get to the heart of your viewer nothing will stop them from gushing about it and doing you the favor of spreading it around. After all word of mouth is the best form of promotion.