Kelli Crist and Tarrin Warren have created a great handbook!!
In this handbook, Kelli and Tarrin detail all of the obstacles from the Ease of Handling Trial. Each obstacle has four sections: The Basics (set up, chart of gaits, riding the obstacle); The Technical (rules, diagram, execution); Judging Criteria (what the judge looks for) and Training Tips (goal, preparation, tips, common mistakes, training exercises).
After the obstacles are all detailed, there is a section on training exercises the rider can practice. The training exercises focus on the things that will make it easier to do the obstacles correctly. This is an excellent resource and should be in everyone's library.