Traveling back to the US on vacation for the 2nd time

Planning on coming to the US for my 2nd visit, what are the required documents i will need at the POE.

The second question is with B1/B2 visa can i get married within a month once am back into the US?

Depends on visa, assuming its B1/B2, you should be able to explain with supporting documents the purpose of visit, for e.g if visiting friends , family should have an itinerary, places you plan to visit, local contacts, return ticket etc.

After 90 days of entering.