Multiple chapter fic's intros should be at least one chapter, or three if you're feeling particularly stingy and want to draw out the plot make the fic longer. Anymore than three will cause the readers to stop reading however, and even three is pushing the limit.
The intro's don't have to get to the point as quickly as a one shot does due to the fact that the intro is at least an entire chapter. Setting up the long term plot. Within a multiple chapter fic there are multiple intro's other than the one introducing the main character ark. There are subplots, therefore there are subintro's. Each subintro should fit whatever subplot your introducing so it may differ in need of style.
There are also introductions to new main characters, or side characters in a multiple chapter fic that need to be addressed. The introduction of those characters depend on the personality of said character that you're introducing, you don't want to introduce a funny character in an extremely serious setting, unless you intend to make that serious setting brighter with their presence.