One thing in our journey that has become apparent, is that what you don't know - can indeed HURT you. at the very least lack of knowledge will slow you down. Learn the laws before you need them. Learn the laws as you need them. But whatever you do, learn the law. It will help you, even if you decided to hire a lawyer.
If you have not faced foreclosure yet you may want to start looking at TILA and RESPA, OR FDPCA laws. If you are delinquent now, or been served a notice of intent to foreclose then start looking at your state's laws and regulations.
IN our state there are laws broken in the process of foreclosure that are common. You can address these before a trustee sale. You need to start documenting everything you can. Here is the link to the AZ Legislature page which has much information including a link to the ARS aka: Arizona Revised Statutes
One MUST READ statute is the one for 33-808. Notice of trustee's sale:
You could find cause to stop the sale.