I saw Kurt Vonnegut speak in 1997 at Florida State University, along with Joseph Heller (who is mentioned in the talk below) and William Styron. Vonnegut was crotchety and slightly addled and either very wise or very flippant or both. As part of the event staff, I remember Vonnegut being very unhappy that he wasn't allowed to smoke in university buildings, so perhaps that accounted for his mood when I saw him. But still, Vonnegut was a huge reason I became a writer myself. Reading Breakfast of Champions as a teenager was a revelation: I wanted this man's job. He was proof that somebody smart and weird and opinionated could write books that meant something, and people would buy those books. (Or at least they would fifty years ago.)
Vonnegut gave many lectures entitled "How to Get a Job Like Mine," and their content varied -- sometimes, as in the videos below, he actually gave some advice to aspiring writers (as well as covering 9/11 and many other topics, though most of them have to do with women and/or dead friends). This lecture was given in 2002 at Albion College, where Vonnegut received an honorary degree. Check it out for some vintage Vonnegut.
Playlist - All 5 Parts
His primary advice for young writers? "Don't use semicolons." I feel like I've already failed; I use them all the time. So it goes.
If the embedded playlist above doesn't work for you, go to YouTube to check out each of the five parts.