This talk of David Evans (@DavidEvans66) was one of my favorites at the Agile Testing Days 2011.
I will only list some things not to find on the slides in this article, and then provide a link to the slides at the end of the article, as they are really self-explaining (imho).
The most essential thing is a human issue: The relationship between testers and programmers, as they are slightly different species. 😉
Companies should create an environmet which enables there employees to continously learn.
The Agile Testing Quadrants are a good way to find out and clearify what kind of tests you’re talking about, if there are differences in understanding of a certain kind of test.
Without taking actions on your test results (or measurements), testing is worthless.
Like in science, testing can only disproove a hypothesis, but never proove it.
The slides are available on Prezi: What Testers and Developers Can Learn From Each Other