Originally Posted by JeffW85

As previously mentioned, the initial CFI is one of the most thorough checkrides you'll ever take. Remember though that you're not only being evaluated on your knowledge, the examiner is also looking to see that you can TEACH. Presentation is just as important as correct information, so make sure you're getting lots of practice presenting the topics. Yes, you need to know everything. Now, having said that, some common weak areas with initial CFIs from my experience:

• Principles of flight - Explaining the 4 forces correctly, proper definitions and relationship, opposing forces are only equal in "unaccelerated flight," etc. Forces in a climb. Induced drag - and not the "by-product of lift" nonsense explanation, most people are not taught it correctly in the first place, then really struggle with it working on their CFI for some reason. Adverse yaw. Make sure you really understand these and can TEACH them.
• Weather - How often TAF's, FA's, etc. are issued and how long they're valid. What condidtions advisories (sigmet, airmet, etc.) are issued for and how long they're valid.
• Airspace - Generally speaking, I never had a CFI student whose airspace knowledge was deficient; but everyone it seemed had a REALLY hard time teaching it. There's alot of information to convey to cover the topic fully and it's easy to get bogged down or to skip items. Make sure you have a usable, easy to follow presentation for this. Draw BIG pictures on the board. Equipment requirements, visibility/cloud clearances, typical dimensions, how it's depicted on a sectional, etc. should all be incorporated at a minimum.
• Airworthiness requirements - Inspections, AD's, service bulletins, maintenance records, definition of airworthy, and so forth. Ensure you know how to use the maintenance records to show that the aircraft is actually airworthy.
• Certificates and documents - In the real world, yes, you'll probably have to look up some of the requirements to earn a certificate from time to time, but for the check ride, you should KNOW them. For priviledges and limitations private vs common carriage and flying in furtherance of a business are typical stumbling blocks.
• Aeromedical - Different types of hypoxia. Chronic vs acute fatigue.

Once again, this is not EVERYTHING, just some common errors. The CFI PTS by itself is somewhat incomplete, to properly prepare you should reference the CFI, Private, and Commercial PTS together. Practice practice practice practice! Then practice some more. The more you run through your presentations the more confident and effective you will be as a teacher, and thus will be successful on your oral. Best of luck!