How you install Rattail can vary somewhat depending on how you intend to use it, but the target operating system (Linux or Windows) will make the biggest difference. It should be noted that while some server software (e.g. Tailbone web app) ought to run on either platform, by far the most development and testing (as well as production installs) is done on Linux. On the other hand, some software will only run on one platform.
Note that while Mac OS is not currently "supported" (has never even been tested to my knowledge), the Linux instructions could hopefully suffice for someone aiming to attempt that. (If you do such a thing and would like to contribute docs, please let me know.)
And don't forget that installation is only part of it. There is still the matter of Configuration.