You can sort lists in many different ways by using the sort icon at the top right of a list:
Shortest & Longest
This will sort items based on their duration estimate.
Procrastinated
This will sort items based on how long you have procrastinated them.
For tasks this means that every day since you first scheduled an item into a day (gave it a "do date") and then delayed doing the task counts as "a day procrastinated".
Most important
This sorts items based on their priority level (colored stars).
Red stars have the highest priority, then orange stars, then yellow stars and finally no star.
Most dreaded
This sorts tasks based on their frog level. The bigger the frog the more you dread a task.
Most urgent
This sorts your list by due dates.
Oldest/newest
This looks at how long ago you have created a task or project.
By Title
This sorts your list alphabetically looking at the title of the task.
By Time
If your tasks include a specific time (e.g. "Call mom 2pm") it will sort your tasks by time. This can be useful to create a chronological order for your daily list.
By Category
This looks at the parent category/project a task is in and sorts it alphabetically based on the parent's name.
This is helpful if you want to group related tasks (tasks from the same project for example) together.
By Label
In the "Labels" strategy settings, you'll find a list of your labels. You can drag and drop them to change their order. When you sort by label, it sorts tasks according to their labels based on the order of the labels in your strategy settings. So if you had labels @A, @B, @C, and @D (in that order), and sorted by label, then all tasks with @A would go before tasks with @B, and all tasks with @A and @B would go before tasks with @A and @C.