Hi @Account Closed I'm a relative newbie as well, but I wanted to chime in since I struggled with the same questions for a long time. I've done a lot of research and reading over the last few months and its finally coming together for me, so I wanted to share with you what I learned.
From what I can understand, the real key to wholesaling a property is finding a true deal - one that no one else knows about yet and one you can get under contract quickly before anyone else does. This may be an REO or forclosure but many experienced wholesalers on this forum are saying these are becoming less and less available. Bandit signs seems to work for many, craigslist ads, working probate, approaching landlords who have just evicted their tenants (they are sick of owning the property) - there are many ways - do more research and you will come across certain methods mentioned over and over that work for many successful wholesales. Learn from the best, don't try to reinvent the wheel. All the answers are on here, or just google wholesaling and you can read a million articles on what others have done successfully.
As for contacting the sellers, it seems a yellow letter campaign might be a good start for you. Just google this or read all the posts on here about them. Its easy and cheap. And effective from what I've read.
Keep in mind that not all investors you want to sell to necessarily want to flip, they may want to rehab/buy and hold, in which case you need to know the numbers inside out and backwards for all possible scenarios. Get to know all the formulas mentioned on the forum for calculating the returns for an investor. Only then will you know if you have a good deal that you will be able to sell easily.
Hope this helps. I know it seems like a lot of work but the return is worth it. Not that I know, I still have to apply everything I'm learning into action! Good luck!