Main Idea Criteria or the Main Idea Smell Test
It is important to remember the four criteria for a good Main Idea so let’s review them now.

You know that you have an acceptable main idea if It passes the Main Idea Smell Test, which is the four criteria that a main idea must meet in order for it to be considered to be well-developed. Your main idea must:
• Be universal (not autobiographical)
• Be able to be expressed in a complete, grammatical sentence
• Assert a singular idea
• Make an assertion that is beyond the obvious and not overly simplistic

If your Main Idea is well-developed, it will often work on two levels: The literal and the figurative. In the literal sense your main idea point may only apply to someone in exactly in the specific set of circumstances discussed in your speech. However your main idea should also convey a figurative or metaphorical point because that is almost always the point that is more universal. As such it is likely to be relatable for a larger number of people. Whenever you can, try to cast your net as wide as possible with your Main Idea, meaning you should use one that conveys the most universal meaning (i.e. the one that could apply to a broader range of circumstances).