This is a certification class, there are no guarantees.  Instructor candidates are highly encouraged to gain a fair amount of paddling experience, take an SWR class, complete their CPR & First Aid certifications, and become an ACA member before taking the IDW/ICE course.  Here are the basic requirements:

• Maturity - Must be at least 18 years old
• Current ACA member
• Be able to complete all IDW/ICE skills
• Effective communication skills
• Manage oneself independently
• Complete the IDW/ICE workshop
• Current CPR and First Aid certification
• Ability to perform all skills listed for your certification level and ability to teach to others

Technical Knowledge

ACA instructors are expected to be very knowledgeable in a large variety of topics.  Take a close look at both the Skills Class and Assessment Class instruction topics.  Do you feel reasonably confident explaining any/all of those topics?  You don't need recite extensive facts and figures, just be able to provide a concise explanation covering key areas - especially safety factors.  Sometimes you will be asked a much more detailed question from a student.  If you don't know the answer, don't fake it.  Jot the question down, research and get back to them.  Teaching is a continuous learning profession.

Paddling Ability

It goes without saying that strong paddling ability for the certification level is a must.  A level 4 instructor only needs to demonstrate solid class III skills in class II - III whitewater.  Adequate seat time before taking this class is essential.  Paddle a wide variety of streams, try tougher lines on easier rapids.  Learn a great deal about scouting rapids.  I highly recommend leading trips at your ability level as this introduces great planning skills.  Finally, concentrate on your paddling form.  Make certain you can demonstrate good J leans, carving turns, proper posture, and smooth paddling strokes.  Practice using the various water features to save energy.

Teaching Ability

 Do you feel comfortable talking in front of a small group of strangers?  A great deal of this is planning & preparation.  Jot a few keywords on your hand or an index  card to help jog your memory.  Avoid the urge to continuously look at extensive notes.  Eye contact not only makes your students more comfortable, they body language can provide clues like I am tired and need a small break or I am totally lost.  Every  teacher has their own unique style.  Just like running rapids, you may need a plan B when your normal style isn't hitting the mark.  I also like to use continuous testing throughout a class.  In my SWR class, I load up the kayak with all my regular paddling gear and have the students dissect it and identify each piece of safety and rescue gear.  This makes the class much more interesting for repeat students and I get plenty of those as well.

Rescue Ability

A level 4 instructor is at least an intermediate paddler.  ALL intermediates should take the ACA SWR class, preferably the full 2-day level 4 class.  At a minimum, make certain you know how to use a throw rope and get some practice.  You will also need to demonstrate a number of other rescue skills like boat based rescues.  This makes a great deal of sense.  A professional instructor should be expected to do what they can to avoid incidents in the first place and respond appropriately should a mishap occur.

Positive Interpersonal Skills

The ACA consistently mentions you need to SELL each skill.  Watch a good salesman in action.  They typically exhibit a cheerful disposition.  They also need to be excellent listeners or they will miss the real interests of their customers.  Be flexible, there are often multiple ways to accomplish given tasks - straps or ropes for tying a boat to a car roof rack for instance.  Occasionally, you will get several experts in specific topics in your class.  Often they will help you out and you can take the opportunity to pick their brains offline.  When talking about first aid kits, I often grab a doctor or nurse whom is in the class to help out - it keeps me honest and they have a great deal more experience with real world experiences.  Sometimes you may need to time box some topics since we have so much to cover in just one weekend.  A tricky area is providing constructive feedback.  Try not to be overly picky, heck - many are learning new skills for the very first time.  Combine positive reinforcement where applicable and warranted.