Put something useful in README.

README.md

@@ -1,2 +1,33 @@
 # Cake.ArgumentHelpers
-Cake aliases to help with consuming arguments and environment variables.
+
+[Cake](http://cakebuild.net/) aliases (methods) to help with consuming arguments and environment variables.
+
+## Getting Started
+
+Just reference the Cake.ArgumentHelpers NuGet package directly in your build script via a Cake addin directive.
+
+> `#addin nuget:?package=Cake.ArgumentHelpers`
+
+## Available Aliases
+
+Yep, just one so far...
+
+### `bool ArgumentOrEnvironmentVariable(..., string name, string environmentNamePrefix, bool defaultValue)`
+
+Since `EnvironmentVariable` always returns a string, it is more complex to involve it in an `Argument` call with a fallback. This alias makes it a single call, hiding away the string comparison done to massage the result to a `bool` value.
+
+It works by getting a boolean value with multiple fallbacks:
+
+1. Try to get it from `Argument` (e.g., command line: `-SomeSetting="true"`)
+2. Try to get it from `EnvironmentVariable` (e.g., `$env:SomeProject_SomeSetting = $True;`)
+3. Use a `defaultValue` if we don't find it elsewhere
+
+#### Example
+
+Given a potential command line argument of `SomeSetting` that could also be set via an environment variable prefixed with a project name, get the boolean value or `false` if it isn't found:
+
+```csharp
+var isSomethingTrue = ArgumentOrEnvironmentVariable("SomeSetting", "SomeProject_", false);
+```
+
+##