Develop your idea. Whether it is born out of a random conversation or a joke you think that works, take the time to figure out how to round it out.
Create likable characters. To increase viewership and keep those viewers interested, they need to be drawn in by the characters you create. Make a backstory for these people, as it will give you something to draw on as the series progresses.
Plot out a season arc. Many creators get lost when they write from episode to episode. Similar to making an outline for a major report, deciding how the characters will grow and change will make the series compelling.
Think about your potential sponsors. The only way to make money on the Web currently is through advertising. With this in mind, make the setting something that lends itself to product placement or advertiser-friendly content.
Write the script and then rewrite it. It helps to work a table read into the process. You can then see where things are working or not working. Adjust the script accordingly so it is as tight as possible.
Build in cliffhangers. Having small "What will happen next?" moments from episode to episode and a large cliffhanger for the season ending will keep your numbers consistent. This is important for wooing advertisers. They want to know viewers are returning.