You can sequence the tasks to be performed within a request by using task dependency mapping. Dependency mapping restricts users from closing tasks until the dependent tasks are closed. Task dependencies are important, because sometimes the result of one task will form the input details for the following task.
To understand the task dependency mapping, familiarity with the following terms is essential.
The first task in the sequence on which other tasks depend is called the parent task. The dependent tasks cannot be closed until the parent task is closed.
Tasks dependent on the parent task are called child tasks.
Go to Tasks inside the request details page and click Dependencies. The Task Dependency page is displayed.
Let's say we have defined five tasks for providing services for the new hire as captured in the screen below:

As you can see, to set up the user computer, the location needs to be arranged first. Similarly, entry in Active Directory is a prerequisite for setting up email address and account in Issue Manager.
Hover the mouse pointer over a dependent task, for example, Setting up email address and click Select Parent.

Tasks eligible to become the parent task will be displayed in green boxes. Click a task and the task will be marked the parent task.

Click Entry in Active Directory, which is the immediate parent for the selected task. The task will be sequenced.

Then, hover the mouse pointer over the task Setting up account in Issue Manager, click Select Parent, the click Setting up email address, thus:

Similarly, mark dependency for other tasks and the final mapping looks like this:

We can infer from the sample dependency mapping that, the two tasks directly branching from the request can be performed simultaneously, while the other tasks must take place in the defined sequence.
At anytime you want to revisit or delete the dependencies, hover the mouse pointer over a dependent task and click Remove.

The parent tasks associated with the selected task will be displayed in red boxes. Click a task and the dependency will be removed.
You can zoom in/out and export the page by using the icons displayed at the top right corner.