A best practice is to ask the next new person to keep notes of obvious questions/unclear details to put in an internal, secure wiki. The issue, as founders, we often don't think about what is obvious to us when we deployed an app and all the server tweaks necessary to get it going, for teaching someone else or replicating what was done. Then, they learn some things and put them into the wiki. Rinse-later-repeat until there's few/no questions as the team grows.

It's continual DR/BCP housekeeping: architecture diagrams, instance inventory/config and other critical info (contact / escalation info) updated so that it's run-over-by-a-bus and EC2-burns-down (almost) resilient.

As you scale, having someone put server config all in Chef or Puppet (cfg management stored in git) will also help reduce deployment pain at the expense of initial setup pain. Initially, a wiki page containing a giant shell script for each server box kind is usually a faster hack.