How to install arara with MiKTeX / Windows?

Well, it depends on which distribution you use:

1) TeX Live 2012: Just update via Package Manager, arara is part of TeX Live 2012.

2) MikTeX: Under the assumption that MikTeX does not provide arara (I only use TeX Live) do

a) Get the installer from BinTray, under the Downloads section (at the time of this writing, the current version is 3.0)

b) Run the installer. After the installation open a command line window and type arara

If you get the following, the installation was successful:

C:\Users\Uwe>arara
  __ _ _ __ __ _ _ __ __ _
 / _` | '__/ _` | '__/ _` |
| (_| | | | (_| | | | (_| |
 \__,_|_|  \__,_|_|  \__,_|

arara 3.0 - The cool TeX automation tool
Copyright (c) 2012, Paulo Roberto Massa Cereda
All rights reserved.

usage: arara [file [--log] [--verbose] [--timeout N] [--language L] |
             --help | --version]
 -h,--help             print the help message
 -L,--language <arg>   set the application language
 -l,--log              generate a log output
 -t,--timeout <arg>    set the execution timeout (in milliseconds)
 -v,--verbose          print the command output
 -V,--version          print the application version

Note that java needs to be installed, you can check with java -version on the commandline. IIRC arara adds itself to the PATH, if however you get a 'command not found' error, add arara's directory to the Windows path. More information can be found also in the arara manual

PS: I'll show arara also next week on the DANTE spring meeting in Gießen.

MiKTeX (2.9, at least) provides arara package.

For installing it, just open the MiKTeX Package manager and filter on arara:

Then go to Edit --> Select Installable Package:

Task --> Install...:

Click on OK:

At the end of installation click on Close:

Et voilà: