I am in the process of making some major WAN/Data Center network changes. As part of that, i am installing
dual ASA5545x's in each DC (2) for redundancy. Please advise on what is best practice for basic configuration on these devices.
If you want a good overview guide, there's a Cisco Validated Design (CVD) that covers an ASA setup. See this link.
At the same time, firewall configuration and what you setup depends a lot on your policy and what you're using the firewall for - Internet edge, DMZ, milti-tenant, inter-department, remote access VPN (client-based and clientless), site to site VPN, etc.
Each has numerous options and no prescriptive guide covers them all.