California Pre-Foreclosure advice! I need some guidance

[Kristoffer Tier]

I am currently in Southern California (San Bernardino and Riverside Counties) and I'm looking for advice from anyone in the SoCal that has experience in dealing with Pre-Forclosure properties. I know that California is a Deed of Trust state so I am looking for information on how I can go about marketing (I was thinking about knocking on doors first), speaking with these type of sellers and the acquisition part overall.

So a couple questions that I have are..

What's the difference between Notice of Default and Notice of Trustee sale? Can I get these properties under contract from the sellers directly when they have these notices? or do I have to go to the bank? 

and are there any legal restraints that I should be aware of before pursuing this niche? 

I don't know what I don't know so any advice or info is greatly appreciated!!!