What to do after seller agrees to sell?

I'm just getting started as an investor, and hopefully going to get past the analysis paralysis. I have a mailing list prepared, a phone they can call, and llc paperwork in process. But what is stopping me from sending the letters/ posting ads, is I have no clue what I would do if I give someone an offer and they accept. How do I close the deal? Do I need title companies, what paperwork do I need, etc. That kind of thing.

Where would I be able to find resources for this information? or can you provide it?