I haven't written a lot of second episodes -- just two (and one of them aired as #1 in the US, and the other aired as #4!). But DMc is dead on in this post on the problems that confront you in writing the episode after the pilot
You may not be in any immediate danger of writing a second episode yourself. But the issues in facing a second episode are much like those in writing any spec. You have to show the brilliance of the template and create a story that arises naturally out of it. You have to come up with a story that only this show can tell.
(In fact about the only thing you don't have to do in a spec that you have to do in a second ep is recap who all the characters are for the audience members who missed the pilot.)
Labels: spec pilots