What shall I preach on Sunday?

 Well, the good news of Jesus from the Bible, of course. 

But which text? What is the unit? Which of the lectionary readings? One or more? How many readings are you going to have and will you mention them all?

The great thing for the preacher is that he never starts with a totally blank page. He starts with a text. 

And I am tempted to spend too long on deciding what that text will be. 

Much better, in my experience, to have a starting point, a plan, rather than to start with the whole Bible. 

Consecutive preaching through a book of the Bible is undoubtedly the best norm for following the argument and intention of the inspired writer. 

How long should the passage for this week be? Inevitably this is guess work. You might only know after you've preached your next too sermons. Get some help from other sermon series or commentaries which will offer outlines of the book. I am probably tempted  to make the sections too long for fear that I won't have enough to say, but it doesn't matter too much. Hopefully my sermon series will be better the second time I preach through this book. 

But sooner rather than later get to work on the actual preaching rather than worrying about what to preach! Pick a section and go for it.