Mostly agree, but I add more.

1. end all your lines C-style; this may save your life many times;

2. declare -is variables and -r CONSTANTS at the beginning, again, C-style;

3. print TIMESTAMP="$(date +%Y-%m-%d\ %H:%M:%S)"; where appropriate if your script logs its job;

4. Contrary to OPs reommendation I strongly try to stick to pure SH compatibility in smaller acripts so they can run on routers, TVs, androids and other busybox-like devices; BASH isn't everywhere.