Show me the Code
I'm lazy when it comes to code. Not in a bad way, but in an efficient way. I want to get to the crux of the matter quickly and move on. Truth be told, that's why I like TDD-I don't have to remember anything more than I need to know right now. My tests remember everything else I knew, but I digress.
When I start evaluating a new library to see if its something I want to use, code is what I want to see. Sure, tell me what it does, briefly, then move into the basic use-case. As an example, consider the front page of Ruby-Lang.org.
You've got access to all the information you need, but right up front and center (almost literally) is some code showing you how to use Ruby.
If you're starting a new library, make sure to put the code right up front. I know there are any number of projects I have on GitHub that fail this test, but I'm not out purchasing domain names and designing custom sites for my projects either. If you bill your project as a€oeasya€¯ and a€opowerfula€¯, show me, don't tell me.
Otherwise, you're no better than the phone commercials] that promise the world will bow before me if only I use their phone, without, you know, showing their phone being used.