Some schools have a set substitute teacher folder list that teachers must follow, while others don't standardize it. As a teacher who has worked both as a classroom teacher and as a substitute, I can say that if your substitute folder contains everything in this list (and some of the comments below also give some good ideas that are less essential, but nevertheless useful), I would feel better about how the day should go.
This guide is aimed at substitute teachers, but I advise regular classroom teachers to look it over as well. Not only will it give you an appreciation of what substitutes often have to keep in their back pocket, but you can get ideas of things to leave as a teacher to make sure that your plans and substitute supplies are useful to the substitute (and therefore useful to your students, too!)
A list of tips that is targeted at substitutes, but it's got some good information that teachers can keep in mind. As another tip to add to the topic of listing duties, I would strongly recommend listing the names and room numbers of other teachers, especially neighbors or other content area teachers, who the substitute can ask for help. Not only do they know the routines, but they also sometimes had good resources if there was no plan or the lesson ended early.
This guide is meant for the classroom teacher, though it is also important to note that if you are using a strategy such as this in your sub plans. A good substitute will keep that in mind while writing feedback. It gives a good idea of how to prepare a classroom for a substitute teacher to minimize problems on the day of the teacher absence.
I found this article to be incredibly helpful for teachers to be aware of. The last thing many teachers want to see is a bad report, especially if you know one or more of your classes can be particularly challenging. There are a lot of time-tested tips that the writer used to get rid of some of his nerves about how his students would behave and improve their overall experience with the substitute. The class and the substitute will thank you for following the advice!
There is some information on this site for administration trying to make their buildings more friendly for substitutes, links to teacher advice, and an odd but entertaining fable in the video about a school that does everything wrong in order to show just how badly a substitute's day can go if the school isn't prepared. Overall, it's not as useful for the teachers themselves, but the resources are worth looking into.