What's your auto-complete setup?
Recent versions of Vim include a built-in auto-complete feature, and of course there are a half-billion other auto-complete plugins available through GitHub.
What's your setup? Plugins, or vanilla? Suggested tweaks?
:se incsearch :se hlsearch
then watch your regexes in action in real-time when you search or search/replace stuff.
It's nothing groundbreaking but I literally couldn't live without those two options.