Writing copy text that’s easy to read is, well, not easy. Especially Germans like me tend to build long nested sentences. Fortunately there are simple mechanical tools like, e.g., the Automated Readability Index. It counts the sentences, words, and letters in a text and returns an estimate on how difficult it is to read. The number it spits out correlates roughly to the US grade level.
To make it easier for myself to use the ARI in any context, I have wrapped it into an OS X service: Calculate Readability. Once installed you just select the text in question and call the service, either via the Services or the contextual menu. I have assigned it a convenient keyboard shortcut (^⌥⌘R), similar to this tip.
If you feel your texts could use a readability check, download the service here. It’s built with Automator and AppleScript, open-source, and free to use.
P.S. This text is readable for grade 9 or higher.