Writing YAML pipelines from scratch can be complicated when you are just getting started. There are two tools available that can help you.

First, there is the option to export YAML from the visual designer. For every task, there is a link with the View YAML title. This opens a small pop-up box that shows you the YAML corresponding to the task and configuration that you currently have open. The same can be done for jobs and, under specific conditions, for complete build definitions.

The other tool available for writing YAML is the built-in YAML editor:

Whenever you open a YAML build definition, there are two tools available to help you. First, there is autocompletion for every location in your YAML file. This shows you the options available at that point in the file. As well as this, there are snippets available in the task picker on the right. When selecting any of the tasks on the right, you configure them visually and then click the Add button to add the generated YAML to your definition.

These two tools aim to bring the ease of the visual designer to the YAML build experience as well, combining the best of both worlds.