One useful definition of "worldbuilding" is the construction of a sense of world on the page. I like to use this definition because I feel that the word "setting" fails to capture the active process that authors engage in. In order to build a sense of world, we have to use several tools - implying world in the actions and judgments of characters, for example, or in their dialogue. Of course, the most obvious and straightforward (if not complete) way to accomplish worldbuilding is through descriptive exposition in the story text.
I am going to call this descriptive exposition rather than "infodumping" because in my view, the latter is simply the former done badly. We definitely want to avoid "infodumping," yet descriptive exposition is quite critical to the success of our worldbuilding.
I've written before about how to get this exposition done with as much finesse as possible, but this summer I had a different aspect of exposition brought to my attention:
When is the best time to include worldbuilding information?
As finely wrought as any verbal carrier of worldbuilding information is, it won't work well if it's stuck in the wrong place. As a general rule, the beginning of a story is better for exposition than the end, and high action or high tension spots are not good for it. There are possible exceptions, of course, such as whenever a new environment is introduced, and the author must take some time to establish the parameters of that environment.
But the general principle is quite a strong one. I'll give you an example. I was working on revisions of my novel, For Love, For Power, and my agent suggested that I should put in a bit more explanation of the Varin pantheon. I therefore had to go back and try to figure out what might be the best place to add in this information. Two possibilities suggested themselves: one in Chapter 3, where my MC Tagaret went to visit a chapel that had been converted into a concert hall, and another in Chapter 15, where Tagaret went to visit someone's home for the first time. I was intrigued by the idea of putting the description in Chapter 15, using statues of deities in the home both to elaborate the pantheon and to demonstrate the host's desire to hide his affiliations with musicians by publicly displaying an icon of a non-musical deity.
Though the idea of using statues for multiple story purposes was more interesting than simply sticking them in the converted church, it really didn't fit. By that time in the story, there was just way too much going on. My protagonist had just come under threat, and had no room in his thinking for noticing anything like a statue. It would have been irrelevant to him, and therefore he would not notice it at all. Making him do so would have been entirely unnatural.
So I went back to Chapter 3, and sprinkled the information in carefully. I started by establishing an overall paradigm for the deities by referring to them as the Holy Celestial Family (which gives readers a sort of filing cabinet to store forthcoming information on the pantheon's members). Then I had Tagaret discover one deity on the way in, and once he was there, explore different areas of the chapel as the action progressed, so he could encounter different deities in each place but eventually cover all the critical pantheon members.
The whole experience got me to thinking about information distribution through a story. I think of it a bit like a river (this one is from Wikipedia):
the creation of a surfable wave in a Czech river).
So this means that you should avoid putting exposition in anywhere that action must occur. Keep it to a minimum in critical set pieces where the reader's attention needs to be on events and how they are occurring. If there is some piece of information about the environment which readers must critically receive in order for the set piece to work, put it in earlier: have them discover the environment in some way before the set piece fully takes off, or seed the information into the narrative even earlier.
It's something to think about.