Here are the 2018/19 USA GMGs.  You can also find them here and from the USA Rugby referee resources page.  USA Rugby puts this document out each year as a guide to how various aspects of the game are to be refereed.  This is the document that answers the question "when is the ball out?", among others.

USAR has promised an updated GMG for 2020, but I haven't seen it yet.

In May 2019, World Rugby published guidelines for dealing with high tackles and shoulder charges.  The framework document lives here or in the pdf attached.  WR says:

Under Law 9.11, the referee is always entitled to issue a red or yellow card for anything that they deem to be reckless or dangerous.

However, the following guideline is intended to improve consistency in application of sanctions by distinguishing between dangerous tackles that warrant a penalty, yellow card or red card. The framework also supports protection of the head of both players by consistently and frequently sanctioning the tackle behaviour that is known to be the highest risk.

Here's a post from the MidSouth Rugby Referee Society site on communication.  http://msrrs.org/2018/02/17/effective-referee-player-communication/

Here's an article about EmHsieh, who is now the New Zealand women's referee development manager.  But I knew her when...

https://www.stuff.co.nz/sport/rugby/119535052/meet-emily-hsieh-the-american-referee-living-the-dream-with-new-zealand-rugby

I suppose the first thing to look at is the laws.  World Rugby posts the current laws along with a lot of ancillary information on their site.  https://laws.worldrugby.org/ 

There's also the Playing Charter and Foreword (really, read them), application guidelines, law clarifications, referee signals, variations, and something called XRugby that I have no idea what it is.  You can also get the laws (but not most of the other stuff) in an iPhone app.  They might even still print the laws in a little book, but if they don't you can print it yourself from the pdf below.

 OK, let's start with Mike Cobb's scrum video from 2014.  Cobber walks you through some stuff about the scrum setup and then shows some video clips of scrums gone bad with commentary about why.  It's a really good intro to refereeing the scrum.

Hi.  I'm a rugby referee based in the Boston area.  I'm using this page to collect referee development information, including stuff about law, game management, application to different aspects of the game, and whatever other rugby refereeing stuff I find.  The focus is on American rugby, but I'm sure much (maybe most) of the content will be from other countries where they play more rugby.

Here's a link to the New England Rugby Referee Society, my local society:  http://www.nerugbyrefs.org/