DON'T ASSUME - ASK

The most basic due diligence that you must perform is to read the contract BEFORE signing it.

I was approached by a couple for help to get out of a listing agreement they had just signed.

They assumed the Realtor included all the key points that were discussed.

To their dismay and frustration, the terms of the contract were different than what they expected. 

My dismay is that this couple reached out for help after the fact.

If you can spend hours researching what type of appliance or vehicle to buy, then spend the same amount of time or more on higher valued assets like your home.

This helpful link provides 101 typical due diligence questions to ask, but remember that every situation is unique and to keep asking questions until you get satisfactory answers.

Never assume the obvious is true. (William Safire).