The first act is the easiest to plot. The second act is always the hardest to plot. Generally a good, you know, sometimes the third act can be difficult because you can get into a rut in the third act - everybody runs to their Corvette, has a chase, and you catch the bad guy.
I believe in three-act structure. When I say that to novel people, or people in the world of books, they go, 'Well, that's a film thing.' However, even a good joke has three acts.
Everyone starts out desperately trying to make a hit, but some people are just more mistake-prone than others. I happened to be fairly mistake-prone. Of the 40 shows I made, I'd say ten were hits, which is a pretty good average.