I draw boxes and arrows. Sometimes the boxes are rounded.

There was a study on this, UML in practice by Marian Petre. http://oro.open.ac.uk/35805/8/UML%20in%20practice%208.pdf where she interviewed 50 developers across 50 companies. Here's what she found.

- 50 interviews.

- 35 people don't use it.

- 11 use it selectively, just whatever is useful.

- 3 use it just once in a project, to generate code.

- 1 uses it to comply with customer or management requirements.

- 0 use it fully.