1. composer and git installed in PATH
2. account on magento.com and github.com and the credentials at hand (github-auth-token)
3. meet the required specs of magento2 (should be okay in recent xampp)
4. enable extension=php_intl.dll in php.ini

Note: i am using git bash so the paths are /c/ instead of c:\ as it runs a unix shell or cygwin

$ cd /c/xampp/htdocs
$ git clone https://github.com/magento/magento2-community-edition.git magento2-test
$ cd magento2-test
$ composer install 

Composer installer asks for auth data for magento.com and github.com and takes a while..

1. have an empty db ready, eg. magento2_test

$ ./bin/magento setup:install --db-name="magento2_test" --db-user="MYDBUSER" --db-passwort="MYDBPASS"
 --admin-firstname="MYFIRSTNAME" --admin-lastname="MYLASTMANE" --admin-email="MYADMINEMAIL" --admi
n-password="MYADMINPASS" --admin-user="MYADMINUSER"

take note of the admin url (you can review/change it in etc/env.php)

 $ ./bin/magento setup:static-content:deploy

this will also take a while

Well, and off you go

$ ./bin/magento indexer:reindex
$ ./bin/magento cron:run